Wave a is being decreased in temperature, and wave b is moving from a liquid to a gas medium. which statement can be made about both waves?
they will speed up.
they will increase the density of their medium.
they will slow down.
they will decrease the density of their medium.

They will slow down.

Explanation:

In the first case, the temperature of the medium of wave A is decreased. This means that the vibration (or the motion) of the molecules of the medium will slow down, and since the wave is transmitted through the vibration of the molecules, this means that the wave will slow down, since it will be propagated slower.

In the second case, the wave moves from a liquid to a gas. In a gas, particles are more spread apart compared to a liquid, therefore the transmission of the wave from one particle to another occurs with less efficiency (because there are less collisions between the molecules), and so the wave will slow down in this case as well.

e/c, where e is its total energy