Let's solve this by subst. (-2/3)x for y in y=2x+8.
Then 2x+8 = (-2/3)x. (For clarity you must use those parentheses.)
The LCD is 3. Mult. both sides by 3, obtaining
6x+24 = -2x. Then 8x = -24, and x = -3. Now that you have a value for x, subst. this value (-3) into either of the given equations to determine y.
Then write your solution in the form (-3, ?? ).