Solve x+y=8 and 2x+y=11 using substitution
You have a choice whether you want to substitute for x or y. I look at both equations and I notice that the second one has 2x + y, so it might be easier to substitute for y.
In the first equation, let's solve for y. x + y = 8, subtract x from both sides
y = 8-x
Now in the second equation, use (8-x) in place of y: 2x + y =11, so 2x + (8-x) = 11
Solve for x. 2x -x + 8 =11 Combine x terms
x+8 = 11, subtract 8 both sides.
x = 3
Now that you know x =3, substitute that in for x in either equation and solve for y. Once you know BOTH x and y, you have the solution. The coordinate (x,y) represents where the 2 lines will intersect.