Hello!
He will miss it by ≈ 0.852 m
Begin by finding the amount of time necessary to hit the target. Use the formula t = d / s:
t = 75 / 180 = 0.4167 sec
Use the equation d = vi + 1/2at² to solve for the amount the bullet will miss the target. (vi is 0 in this instance). We are solving for the vertical component, so use a = 9.81 m/s (gravity).
d = 0 + 1/2(9.81)(0.4167²)
d ≈ 0.852 m