Boyle's, Charles', and Gay-Lussac's Law can be combined together for calculations in which more than one of the properties of gas change.  Look in your text p.453-457 for help with this.
Homework:  p.457 #18-21

All calculations involving gases must have the temperature in kelvins, not in degrees Celsius.  Volume and pressure are both directly proportional to kelvin temperature.  Text reference is p.436-449.
Homework:  p.446 #5, 6, 8, 11; p.449 #13; p.451 #4