Step 1) Solve the first equation for y:
3x - color(red)(3x) + y = 5 - color(red)(3x)
0 + y = 5 - 3x
y = 5 - 3x
Step 2) Substitute color(red)(5 - 3x) for y in the second equation and solve for x:
x - 2(color(red)(5 - 3x))= 11
x - (2 xx color(red)(5)) + (2 xx color(red)(3x))= 11
x - 10 + 6x = 11
7x - 10 = 11
7x - 10 + color(red)(10) = 11 + color(red)(10)
7x - 0 = 21
7x = 21
(7x)/color(red)(7) = 21/color(red)(7)
(color(red)(cancel(color(black)(7)))x)/cancel(color(red)(7)) = 3
x = 3
Step 3) Substitute color(red)(3) for x in the solution to the first equation at the end of Step 1
y = 5 - (3 xx color(red)(3))
y = 5 - 9
y = -4
The solution is x = 3 and y = -4