Calculate the maximum height using the initial speed, half-time, and angle. The initial speeed is 9.8m/s, half time is 1.8, and the angle is 75.
Good Lord. Ok, I assume you are a beginning kinematics student, and you are looking for the height when a projectile is launched slightly upwards, knowing only the time from launch to max altitude. But honestly, your given initial speed is hightly suspect. I will go with it.
h=vi*t-1/2 g t^2
h=9.8*1.8 - 4.9*1.8^2=1.76 meters. about ceiling height if launched from a student desk.