Question

8.7 is 56% of what number

Answer 1

8.7 is (means =) 56% of x (x is the name of "what number")
8.7 = 56/100 * x
multiply both sides by 100/56
100*8.7/56 = x
870/56 = x
can you finish ?

Answer 2

15, thank you

Answer 3

I would say 15.54 (rounded to the nearest 100th)

Answer 4

or 15.5 rounded to the nearest tenth