First, you would write the fraction 10/100 because it is 10 percent out of 100. Then you would write the fraction 5/? because 5 is the portion, and the question mark stands for the whole. Now, find the number that you can multiply 5 by to get 10. The answer is 2. Which means 10 divided by 2 is 5. Now divide the denominator. 100 divided by 2 equals 50, so her whole allowance is 50 dollars.