Question

One of Gemma's 5 friends is going to upgrade to a newer device soon. The average cost of their devices will then increase to $663 from the previous $657. How much more expensive than the older one is this newer device?

Answer 1

Old value of 5 devices = 657
New value of 5 devices = 663

Increment cost of 5 devices 
663 - 657 
6

Therefore the increment for one device
6 / 5
1.2