How do you solve nuclear reaction equations?
You basically have to make sure the numbers of protons and neutrons add up on both sides of the equation.
It helps to know the identity of the particle that is emitted. If its an alpha particle, beta particle, positron, electron capture process - in all cases, you have to know the identity of the particle (or deduce it from other info) and balance out the protons and neutrons.
It also helps to know where these particles come from. Simplistically speaking, a beta particle (simple electron) comes from the nucleus (think of a neutron as being a fusion between a proton and an electron....if you rip that electron away, you have turned that neutron into a proton).