Answer:
15. Add 5 to both sides
Divide 2 on both sides
16. Add 7 to both sides
Divide by 3 on both sides. This is what it wants you to say but the answer is wrong. If you want to correct your teacher say the answer is actually 54 because you have to multiply by 3 on both sides. 18 times 3 is 54
17. Multiply by 4 on both sides
Divide by 9 on both sides