Final answer:
The percent of students who play the trumpet is 36%.
Step-by-step explanation:
To find the percent of students who play the trumpet, divide the number of students who play the trumpet by the total number of students who play a brass instrument and then multiply by 100.
In this case, there are 18 students who play the trumpet out of 50 students who play a brass instrument. So the percent of students who play the trumpet is:
(18 / 50) * 100 = 36%