Two spaceships are traveling in the same direction. With respect to an inertial frame of reference spaceship

Question:

Two spaceships are traveling in the same direction. With respect to an inertial frame of reference spaceship A has a speed of 0.900c. With respect to the same inertial frame spaceship B has a speed of 0.500c. Find the speed vAB of spaceship A relative to spaceship B.