A rock thrown with speed 7.00m/s and launch angle 30.0 (above the horizontal) travels a horizontal distance of = 9.00m/s before hitting the ground. From what height was the rock thrown?
Use the value = 9.810 for the freefall acceleration.
Use the value = 9.810 for the freefall acceleration.

If you actually mean the range to be 9 meters, the launch height
h = 5.62 m
h = 5.62 m

It travels a horizontal distance of = 9.00m
time = 9 / [7* cos 30] = 1.48s
vertical motion
s = ut + 0.5 * at^2
s = 7 * sin 30 * 1.48  0.5 * 9.81 * 1.48^2
s = 5.56 m
the rock was thrown from a height of 5.56m answer
note: negative sign denotes distance opposite 7m/s.
time = 9 / [7* cos 30] = 1.48s
vertical motion
s = ut + 0.5 * at^2
s = 7 * sin 30 * 1.48  0.5 * 9.81 * 1.48^2
s = 5.56 m
the rock was thrown from a height of 5.56m answer
note: negative sign denotes distance opposite 7m/s.