Please i just want the answer for the boxes if you know the right answer please tell me please

Athe top of a hill, an athlete on a skateboard has x joules of mechanical energy. how much mechanical energy will she have at the bottom of the hill? ignore the effects of friction.

The density of benzene at 15 °c is 0.8787 g/ml. calculate the mass of 0.1500 l of benzene at this temperature. enter your answer in terms of grams

How many grams of ammonia would be produced by the decomposition of 16.93 mlof hydrazine? (the density of hydrazine is 1.021g/ml)