A local electronics store will sell 7 AC adapters and 3 rechargeable flashlights for $84. what is the price of a single AC adapter and a single rechargeable flashlight?

We know that the cost of 7 Adapters is a multiple of 7

and the cost of 3 flashlights is a multiple of 3, and together they add up to 84

Multiples of 7: 21, 28, 35, 42, 49, 56, 63

Multiples of 3: 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51, 54

Find the the multiple of each which add up to 84

A little research reveals $21 for 3 flashlights, and $63 for 7 Chargers

$9 for a charger and $7 for flashlight