Question

Solve the following proportion. 15/21=5/x
A. 3
B. 105
C. 7
D. not given

Answer 1

15/21 = 5/x
15 * x = 21 * 5
15x = 105
x = 7

Answer 2

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.