Asporting goods store sells triangular team pennants in two sizes. the base of one pennant is 18 in. and the length of the side is 9 in. the other pennant is similar to the larger pennant and has a base that is 6 in.

what is the length of the side of the smaller pennant?

This is a proportion problem because the problem stated that the two team pennants are similar.

Pennant 1 = base = 18 in ; length = 9 inches
Pennant 2 = base =   6 in ; length = x ?

9/18 = x/6
9*6 = 18x
54 = 18x
54/18 = x
3 = x

The length of the  side of the smaller pennant is 3 inches.