How do I calculate the change in energy of an electron transition?
When an electron transitions from a higher energy state to a lower energy state, the energy has to go somewhere. Usually it is emitted as light of a given wavelength which corresponds directly to the change in energy of the electron.

The energy of light at a given frequency $\nu$ is 
$$ E = h\nu\; , $$
where $h$ is Planck's constant.
The frequency of light is directly related to the wavelength $\lambda$ and the speed of light $c$ via
$$ c = \nu\lambda\; . $$

Combining these two equations we get
$$ E = \frac{hc}{\lambda}\; , $$
with which you should be able to calculate the $\Delta E$ values for the transitions.