Free brainiest just tell me what 9+10= :)

During the 1920s, which president atoped a laissez-faire toward business, which bring about great depression

The president has the power to grant pardons . true or false

Ascientist performs an experiment where she measures the mass of a piece of metal, pours acid onto the metal, washes the metal, and then re-measures the mass of the metal. the scientist repeats the experiment several times, each time increasing the amount of acid used. the dependent variable in the experiment is the: initial mass of the metal final mass of the metal amount of acid used washing the metal