Jo's mother, Anne, is four times as old as Jo. In four years time, Anne will be three times as old as Jo. How old is Jo? (this is an easier version of a riddle we'll do in AP CS)

Jo's age = x = 8 years

Step-by-step explanation:

Let

Jo's age = x

Jo's mother, Anne's age = 4x

In four years time, Anne will be three times as old as Jo.

Jo's age =3( x + 4)

Jo's mother, Anne's age = 4x + 4

How old is Jo?

Equate Jo's age and his mother's age

3(x + 4) = 4x + 4

3x + 12 = 4x + 4

3x - 4x = 4 - 12

-x = - 8

Divide both sides by -1

x = 8

Therefore,

Jo's age = x = 8 years