Question

The ratio of pens to pencils is 7:9. If there are 27 pencils, hoe many pens are there?

Answer 1

7/9 = x/27

Cross multiply and solve for x.

Answer 2

or, you can think of it like this

27 = 9*3, so

7:9 = 7*3 : 9*3 = 21:27