y=2x-3 an x+y=3
subsitution
since y=2x-3, put (2x-3) wherever you see y
put taht in the other equation
x+y=3
x+(2x-3)=3
x+2x-3=3
3x-3=3
add 3 to both sides
3x=6
divide by 3
x=2
subsitute back
y=2x-3
y=2(3)-3
y=6-3
y=3
so the solution set in (x,y) form is (2,3)