H = number of hours Harry worked
A = number of hours Aiden worked
Harry worked 7 hours last week so we know H = 7
This is one third as many hours as Aiden's time working so H = (1/3)*A
We can multiply both sides by 3 to get 3H = A or A = 3H
If H = 7, then...
A = 3*H
A = 3*7
A = 21
Answer: Aiden worked 21 hours
