Question

0.75% if what number is 10

Answer 1

Do you mean "What is 0.75% of 10?" If so, then:

0.75% × 10 
0.0075 × 10 
0.075

And if you mean "10 is 0.75 of what number?" then:

10 ÷ 0.75 
10 ÷ 0.0075 
1333.33

Answer 2

Let the number be x. 
0.75 % * x = 10 
0.75/100 * x = 10 
0.0075 * x = 10 
x = 10/0.0075 = 1333.33