The answer is 16 shirts. (in the equation below, x represents how many shirts he sold.)
We can solve this question by using this equation: 3x + 45 = 93
The next step would be to subtract 45 from both sides, which would leave us with 3x=48.
Then, we must divide both sides by 3. This means 3x divided by 3 = 48 divided by 3. This leaves us with x = 16 shirts.