Question

x=y-1 y=(4-2x) solve by substition

Answer 1

Since you have an equation equal to both x and y, you can either substitute the equation equal to x for x or the equation equal to y for y.
x=y-1
y=4-2x
I would substitute the y in using 4-2x
x=(4-2x)-1
x=3-2x
3x=3
x=1
Then plug in x and solve for y
1=y-1
2=y