Solve the equation 2x + 5y - 3z = -1. Write the general solution as a matrix equation.

Question

I did some guessing and ended up getting this much:

[x]= [-1/2 _ _ ] X [1]
[y]= [ 0 1 0 ] X [s]
[z]= [ 0 0 1 ] X [t]

however I still can't figure out the last two values in the first row