Hello, Makaylahall5!
The least common denominator for 4/15, 1/12, and 3/8 would be 120. To figure this out, just multiply each one of the denominators until they all have the same denominator. So, 15 multiplied by 8 would be 120. 12 multiplied by 10 would be 120. And finally, 8 multiplied by 15 would be 120. So, your final fractions would be: 32/120, 10/120, and 45/120! So, when you add them all up, they add to: 87/120. Now, just simplify this! Divide both of them by 3. Now, the final answer is 40!
~hope it helps :)