Okay, so to find like denominators you need to find a number that both denominators go into. For 15, they both go into 45. 9 goes in 5 times and 15 goes in 3 times. So multiply their numerators by 5 and 3. It would be 25/45 for 5/9 and it would be 12/45 for 4/15. Do the same for 16 and 17, for 16 they both go into 42 and for 17 they both go into 42.
