Answer:
1.)meters of clothes that were not use
91/8m,3 5/6m
subtraction
91/8-3 5/6
9 1/8-3 5/6
9 3/24- 3 15/24
8 24/24 + 3/24=8 27/24
8 27/24-3 15/24
=5 12/24 or 5 1/2m cloth were not used
2.)Parts of cake left
10,3/10
subtraction
10/10 -3/10
=7/10parts of cake left