Dad, can you help me find the lowest common denominator in this problem please ?

Don't tell me that they haven't found it yet, I remember looking for it when I was a boy!

Exciting times this week - We have been furiously achieving credits for the Middle East Maths Challenge.
You could hear a pin drop.

Teacher: Did you parents help you with these homework problems?
Pupil: No I got them all wrong by myself !

Good luck everyone. May the  be with you.