https://www.gregmat.com/quizzes/quiz/timed-quant-practice-easy-section-1-sample-1 (Question 12)
I think the prompt here is ambiguous. The height of 3 is not necessarily the leg of the right triangle unless specified. It could be the perpendicular distance to the hypotenuse of 5, which means the area is (1/2)*3*5 = 7.5