Answer: 90 cheeseburgers had tomato
Explanation:
You know that
of the 240 cheeseburgers The Booster Club sold had pickles. Then, the number of cheeseburgers that had pickles was:
The number of remaining burgers is:

According to the exercise,
of the remaining cheeseburgers had onions, and the rest had tomato (which means that
had tomato).
Therefore, you can multiply the remaining burgers by
in order to calculate the number of cheeseburgers that had tomato. Then, this is: