Answer:
hey hun, I think u need to give us more information on the question. Is that the full question ??
your sister would be 35
Step-by-step explanation:
8/7 x 9/10 is 72/70
7/10 x 9/8 is 63/80
10/7 x 9/8 is 90/56
7/9 x 8/10 is 56/90