Answer:
Jewel is 7 years old
John is 1 year old
Dave is 17 years old
Explanation:
From the question we are told that:
Jewel age is

John age

Dave's age a Year ago

So that Dave.s age this Year could be

Simplifying Equation for Dave's age we have





Dave is 17 years old
Therefore
Johns age is



John is 1 year old