@Markiyan Hirnyk 

Thanks

@Carl Love 

This is true. But in order to find the coefficients I need to know the values of x[1]...x[60]. Simply substituting the functions for the coefficients into the equations and then treating them as non-linear equations does not work.

@roman_pearce 

I'm not sure that would work. My original post may have been unclear, I have edited it to try and explain better. I know what my coefficients are, and I know what they are in terms of x[1]..x[60]. So for example a=x[1]/x[6]. I need to solve the equations to find my x[1]...x[60] and then use these values to find my coefficients. 

@Kitonum 

But then how do I solve the matrix? It is too large to solve symbolically. I want to solve for x₁...x₆₀ in terms of a,b,c,d and then use the solution to find a,b,c,d.

@Carl Love 

Sorry, I should have been more clear a,b,c,d are functions of x₁...x₆₀