Atire dealer sells 2 tires for as much as he paid for 3 tires. he paid $240 for a dozen tires. what is the total profit on 12 tires

First, find how much he paid by tire.
To do so, divide what he paid by how many tires he bought like this :
240$ / 12 = 20$ per tire

Then, calculate how much he sells each tire.
To do so, start by calculating how much he paid for 3 tires:
20$ x 3 = 60$

This is the price he sells 2 tires for, therefore :
60$ / 2 = 30$
he sells his tires 30$ each.

Finally, you have to calculate the profit he made by selling 12.
We already know how much it cost, so you need to find how much money he gets selling them :
12 tires x 30$ = 360$

To find the profit, take off the amount he paid from the amount he made :
360$ - 240$ = 120$

There you go!