Find the least common multiple which is 15. Multiply your whole equation by 15, you should end up with 5x-45 = 3x -75, then it should be a bit easier to isolate X. Subtract 3x from both sides, add 45 to both sides, you'll end up with 2x = -30. Divide by 2, x = -15! Ask if you have any questions.

-Nichole.