Find the mass of a sample that has a dersity of 2 g/mL and a volume of 10 mL

mass = volume x density.

Explanation:

2 x 10 = 20g

The frequency of a certain wave is the quotient obtained by dividing the speed of the wave by the wavelength. That is 
                                          f = s/λ
Substituting the known values,
                                          f = (5.6 m/s) / 3.3 m
                                             = 1.7/s
                                             = 1.7 Hz