Why do you say that the initial velocity is 0, when you are clearly told it's 7 m/s. You aren't asked about the final velocity, so don't be concerned about it. Use the standard equation for distance based on time, initial displacement, initial velocity, and acceleration:
$\displaystyle y(t) = y_0 + v_o t + \frac 1 2 a t^2$
Here y(1.45s) = 0 (because the ball hits the ground at t=1.45s), v_0 = 7 m/s (negative because the ball is thrown downward from the top of the cliff), a = 9.8 m/s^2, and t = 1.45 s. Plug and chug to solve for y(1.45). By the way, the answer is not negative 20 meters  that would mean the cliff is actually a well. The answer should be a positive number.
