How do i solve this can somebody show me how to solve this

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

Which best explains why this triangle is or is not a right triangle ?

Solve the problem by making up an equation. a man could arrive on time for an appointment if he drove the car at 40 mph; however, since he left the house 15 minutes late, he drove the car at 50 mph and arrive 3 minutes early for the appointment. how far from his house was his appointment?