In the term of Names in help, the next sentence was written:

"Any valid Maple name formed without using left single quotes is precisely the same as the name formed by surrounding the name with left single quotes.  Therefore, x and `x` both refer to the same name x. However, a keyword may not be used as a name unless it is enclosed in left single quotes."

And, at the term of Maple Keywords (Reserved Words) in maple help, the fowing is written.

"If one of these words must be used as a name, such as in a call to the help function, it must be enclosed in left single quotes (back quotes) (` `)".

restart;
Eq1:=x+2*y+3*z=9:
Eq2:=4*x+y+5*z=29:
Eq3:=2*x+2*y+5*z=21:
solve([Eq1,Eq2,Eq3], [x,y,z]);

subs(%[][],2*x+3*y+z);

I'm not sure about my answer. So, I will delete it if it is wrong.

>with(LinearAlgebra):
>solve(2*x-3*y+z,z);
>vec:=<x,0,0> + <0,y,0> + <0,0,-2*x+3*y>;
>A:=<<1,1,-2>|<3,4,-7>|<-5,-8,13>>;
>B:=Multiply(A,vec);
>C:=solve({X=B[1],Y=B[2]},{x,y});
>Z=eval(B[3],C);

my_answer.mw

Hello

I hope the following link will be an anwser to your question.

https://faq.maplesoft.com/hc/en-us/articles/360019761511-Testing-command-line-console-Maple

> X:=[seq(i, i=0..0.5, 0.05)]; 
> Y:=[0.486935382154125, 0.485087274176440, 0.483255914856304, 0.481441076124814, 0.479642533998987, 0.477860068520125, 0.476093463645627, 0.474342507167362, 0.472606990609939, 0.470886709216958, 0.469181461771770];

> Z:=zip((x,y)->[(x,y)],X,Y);

Z := [[0, .486935382154125], [0.5e-1, .485087274176440], [.10, .483255914856304], [.15, .481441076124814], [.20, .479642533998987], [.25, .477860068520125], [.30, .476093463645627], [.35, .474342507167362], [.40, .472606990609939], [.45, .470886709216958], [.50, .469181461771770]]

> with(plots):
> pointplot(Matrix(Z,datatype=float),axes=boxed);

> expand(sin(2*x+3*y),2*x,3*y);

sin(2*x)*cos(3*y)+cos(2*x)*sin(3*y)

See as well the next example in the help of expand,

> ee := (a+b)*z + sin(a+b) + exp(a+b);
>expand(ee, op(indets(ee, function)));

z*sin(2*x+3*y)+z*a+exp(a+sin(2*x+3*y))+sin(a+sin(2*x+3*y))

Question_about_GRID.mw

LL:=[[0,1,0],[1,1,1],[2,1,2],[3,0,1]]:
PLOT3D(GRID(1..3,1..2,LL),AXESLABELS(x,y,z),
ORIENTATION(135, 45), AXES(BOXED))

1st element of LL is [0,1,0], 2nd one is [1,1,1], 3rd is .., 4th is ..

In total there is 4 elements in LL. From 4 elements, a partition of x making only three ranges  of x is possible.

And, seeing in the inside of 1st element of LL,[0,1,0], it is compsed from three numbers, 0,1,0. So,

  a partition of y making only two ranges of y is possible.

On the other hand, from GRID(1..3,1..2,LL), the range of x extends between 1..3, and that of y does between 1..2.

So, each partitioned ranges of x has (3-1)/3 in its length, and for y, the length is (2-1)/2.

And, for the 1st element of LL, [0,1,0], it says that for the first value of x, which is 1 from the prescription of GRID(1..3,1..2,LL), 

values of z takes 0, 1, 0 for each y, that is for 1st y which takes the value 1 , 2nd y which takes the value 1.5 , and 3rd y, which takes the value 2. 

And, for the 2nd element of LL, [1,1,1], for the second value of x, for each y, all z takes values of 1.

And, for the 3rd element of LL, [2,1,2], for the third value of x, for each y,  z takes values of 2, 1, 2,  respectively.

restart;
a1:=u(y)=v/d^2*U(Y);
a2:=y=d*Y;
a3:=isolate(%,Y);
a4:=subs(%,a1);
a5:=diff(a4,y);
a6:=diff(a4,y$2);

In Japan, the released day of this year was August 23.
I hope that maplesoft could bestow the right of users like me to use the original, not Japanese version, 
for the while between the original released day in March and the day August 23. 

You can write as

print("A=B=C");

It's due to the difference of eval between when you used that package, which means you are using eval in that package,
and when you don't use that package. If you use some package, you might be using commands in
those packages not that in the global package which is implemented when you begin your session.
In this RealDomain package, there is eval command. If you don't want to use that, you can avoid it
with :-eval brabra. I appended a file.

difference_of_eval.mw

P:=(a,b,c,d,e,f)->a^2+b^2+c^2+d^2+e^2+f^2;
b:=x->x^2;
c:=x->x^2;
d:=x->x^2;
e:=x->x^2;
P(a,b(a),c(a),d(f),e(f),f)=0;
solve(%,a);

I think you had better remove float in the proc()

right click ->Prove Info ->Copy data  Then, paste it onto your editor, then you can see  the data at any ratio zooming as large as you like.

a1:=plots:-contourplot(r*sin(phi), r = 0 .. 10, phi = 0 .. Pi, coords = spherical, grid = [80, 80]):
plots:-display(a1,view=[-10..10, -10..10]);