712 ÷ .10 = 7120. When you divide by a percentage you're multiplying.
7.12
712
178
0.0112
712 divided by8 with all the work = 89
79.1111
89
0.21
1.5 billion divided by 10 percent = 0.15
10 percent of 90 divided by 3 = 3
As 712 is ending by an even digit then it can be divided by 2 thus 712 is not prime
25%