Physics: Bulbs & Circuits?

Your headlights in your car are not working. You check and see that the filament (tiny wire in the bulb) has broken. Your friend suggests fixing it with some glue but that doesn't work. When you go to the store the assistant suggests wiring together 2 bulbs instead of 1 bulb because it will be brighter but each one is only half as bright as before.

a) Explain why your bulb is not working.
b) Why didn't the glue work?
c) Would two bulbs connected bot be brighter?
d) Explain how to connect the 2 bulbs so that they would both be as bright as one bulb without changing the car battery.