subsitute
y=x-8
since y=x-8, subsitute x-8 for y
2x+3(x-8)=1
distribute (a(b+c)=ab+ac)
3(x-8)=3x-24
2x+3x-24=1
combine like terms
5x-24=1
add 24 to both sides
5x=25
divide 5
x=5
subsitute
y=x-8
y=5-8
y=-3
x=5
y=-3 is solution
in (x,y) forom
(5,-3) is the solution