*Where are the Mathematicians?*
A girl went to school and the teacher asked, how old are you? She replied I don't know but I know that I'm half my mother's age.
The teacher asked; 'Ok, how old is your mother'? She said I don't know but I know that my dad is 5 years older than my mother.
The teacher, then asked; 'how old is your dad'? She said I don't know but I know that if we add our ages the answer is 100 years...
Now, how old is the girl, her mum, & her dad?
Please show your workings!