# How do you solve by substitution 2x-y=23 and x-9=-1?

We write the second equation $x = 9 - 1 = 8$ and substitute into the first: $2 \left(8\right) - y = 23$ or $y = 2 \left(8\right) - 23 = - 7$.
Check $x = 8 , y = - 7$
 2(8) - (-7) = 16 + 7 = 23 quad sqrt
 8 - 9 = -1 quad sqrt