What is the equation for work done by gravity for an object dropped to the ground?

Work = MGH where

M is the mass
G is the acceleration due to gravity
H is the height

If you didn't know that formula, you can go from the basic formula;

Work = Force x distance

What is force? Force is mass x acceleration.

Therefore, work = mass x acceleration x distance

where the mass is the mass of the object, acceleration is the acceleration due to gravity and distance is the height from which the object was dropped.

Yes, helpinhere, it's just that we can never be sure at what level of education the OP is. I prefer mention acceleration due to gravity since early classes use 10m/s^2 for the sake of simplicity and later 9.8m/s^2. Thanks for the greenie both of you! :)