Here is one done exactly like yours step by step. Use this as a model.
Multiply through by the least common multiple (denominator) or 9 and 15, which is 45: Checking the answer 180: The ninth part of 180 is or 20 The fifteenth part of 180 is or 12 And indeed 20 exceeds 12 by 8. Now do your problem EXACTLY the same way. Edwin