reduced row echelon form

[zekester]

i have a matrix in reduced row echelon form and it gives me the equations
x1+x2=-27.5, x3=-13.5, and x4 = 15. how do i solve for x1 and x2

[quasar987]

All you can say about x1 and x2 is that x1 = -x2 - 27.5 (or x2 = -x1 - 27.5). That is to say, one of the variable depends entirely on the other. So the general solution for x is that x is any vector whose components (x1, x2, x3, x4) are such that x1 = -x2 - 27.5, x2 = x2 (i.e. any real number) , x3=-13.5, and x4 = 15.