How do you add or subtract complex numbers?

A complex number has the form a+bi. We call a the 'real' bit (ie. the bit on a regular number line) and b is the 'imaginary' bit.
To add or subtract complex numbers you just add the real bits of both together and the imaginary bits of both together. (You CAN'T add a real part to an imaginary part).
For example: what is (3+2i) + (5+4i)?
Real bits: 3+5=8
Imaginary bits: 2i+4i=6i
So the answer is 8+6i