Xavier gave 1/8 of his stamps to Joe, 5/9 of his remaining stamps to Jason and 3/7 of the rest of his stamps to Kim. He then had 16 stamps left. How many stamps had he at first?
Joe got 1/8, leaving 7/8
Jason got 5/9 * 7/8 = 35/72, leaving 7/18
Kim got 3/7 * 7/18 = 1/6, leaving 2/9
so, 2/9 x = 16
x = 72
check:
Joe got 1/8 * 72 = 9, leaving 63
Jason got 5/9 * 63 = 35, leaving 28
Kim got 3/7 * 28 = 12, leaving 16 ✅