Solve the system of equations using substitution y=x-1 and y=-2x+5

Since the two equations equal y, set them equal to each other.

x-1=-2x+5

From there, solve for x.

First get x on one side, by using the addition property of equality.

x-1=-2x+5
3x-1=5

Isolate x by adding 1.
3x=6

Lastly get x all by itself by dividing each side by 3.
x=2

You can now substitute your x-value, 2, into one of the equations (or both, if you wish; either one will result in the same answer.)

y=x-1
y=2-1
y=1

OR

y=-2x+5
y=-2(2)+5
y=-4+5
y=1

Final
x=2 and y=1

Any questions or anything you would like me to clarify, feel free to ask :)