Solve the following proportion. 15/21=5/x

A. 3

B. 105

C. 7

D. not given

15/21 = 5/x

15 * x = 21 * 5

15x = 105

x = 7

If you would like to solve the following proportion 15 / 21 = 5 / x, you can do this as follows:

15 / 21 = 5 / x / * x

15 / 21 * x = 5 / * 21

15 * x = 5 * 21 / 15

x = 5 * 21 / 15

x = 7

The correct result would be C. 7.