Which one of the following statements expresses a true proportion?

A. 2 : 3 = 3 : 2

B. 3 : 5 = 12 : 20

C. 42 : 7 = 6 : 2

D. 14 : 6 = 28 : 18

The answer is B. 3 : 5 = 12 : 20

2:3 doesn't equal 3:2 because they are backwards

42:7 doesn't equal 6:2 because 42:7 simplifies to 6:1 which is not equal to 6:2

14:6 doesn't equal 28:18 because 14:6 simplifies to 7:3 and 28:18 simplifies to 14:9, and these two proportions are not equal