Population Ratio Problem

In a small town, the population is made up of children and adults. The ratio of children to adults is 3:5. If there are 120 children in the town, how many adults are there?

To solve this, set up a ratio based on the given information. Let the number of adults be represented by a.

Using the ratio $$\frac{3}{5} = \frac{120}{a}$$, find the value of a.