A bullet is fired from ground level with a speed of 150 m/s at angle 30 degrees above the horizontal?

A bullet is fired from ground level with a speed of 150 m/s at angle 30 degrees above the horizontal at a location where g = 10.0 m/s^2 . How long does it take before the bullet hits the ground? I know the answer is 15 seconds but how do you solve it. Please plug in numbers with equations. Thanks!!!