y is equivalent to x-11 here, so replace y in the 2nd equation with x-11:
4x + (4/5)(x-11) = 68. Mult. all terms by 5 to elim. the fraction (4/5):
20x + 4x - 44 = 68
Combining like terms, 24x = 112, and so x = 112/24 = 14/3
If x is known, then y can be calculated from y = x-11:
y = 14/3 - 11, or y = 14/3 - 33/3 = -19/3
Then the solution is (14/3, -19/3).
