An astronaut on the planet Zircon tosses a rock horizontally with a speed of 6.00 m/s. The rock falls through a vertical distance of 1.00 m and lands a horizontal distance of 7.00 m from the astronaut. What is the acceleration of gravity on Zircon?

How many seconds does it take the rock to land? (using horizontal speed)

Now using suvat equations for the vertical motion of the rock, you should be able to find a value for a, this is your gravitational value.

Let me know if you need further help.