Answer: 15.
Step-by-step explanation: If one-third of the students are girls, then two-thirds of the students are boys:
number of boys = (2/3) * 30 = 20
Three-quarters of the boys play basketball, so the number of boys in the class who play basketball is:
number of boys who play basketball = (3/4) * 20 = 15
Therefore, the number of boys in the class who play basketball is 15.