A 15-ft ladder leaning against a wall begins to slide. How fast
is the top of the ladder sliding down the wall at the instant of
time when the bottom of the ladder is 9 ft from the wall and
sliding away from the wall at the rate of 7 ft/sec? Hint: Refer to
the accompanying figure. By the Pythagorean Theorem, x2 + y2 = 225.
Find dy/dt when x = 9 and dx/dt = 7. (Round your answer to two
decimal places.)