What are the extremes of the following proportion 3/15 = 12/60

In a proportion there are letters assigned to represent various numbers. a, b, c, and d.

a, b, c, and d are 4 non-zero rational numbers that are terms of proportion.

a/b = c/d or a:b = c:d

a and d are the end terms or known as the extremes.

b and c are the middle terms or known as the means.

With this information, we can gather that the extremes of the following proportion are 3 and 60.

3/15 = 12/60; a/b = c/d

a = 3; b = 15; c = 12; d = 60

3 and 60 are the extremes

15 and 12 are the means