The inside of the car smells like gas fumes when you are driving. What could cause this to happen? Is it an easy fix? Thanks

Many things could cause a fuel smell.
Have you inspected for leaks in the fuel system? Take a look under the car and under hood when you smell the gas. Keep a fire extinguisher handy just in case...
If anything begins noticeably leaking, shut it off and place a catch pan under the leak if possible.