What method is being used when playing minecraft or legos?

Which  was not a problem faced by farmers in the late 19th century

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

Prior to which amendment were slaves counted as three-fifths of a personality