Respuesta :

AnonymousGiantsFan
You make a common denominator by going like this:

3: 3, 6, 9, 12, 15
5: 5, 10, 15
You found common denominators!
Need more, ask me :)
GraceAnnH
1          4             5        12
_          _     =      _         _
3          5            15       15             and now just do the math