Amanager purchased a total of 21 coffee mugs and key chains. each coffee mug cost $8.50, and each key chain cost $2.75 . if manager spent total of $132.50, how many coffee mugs did the manager purchase solve this

Let m be the coffee mugs and k be the key chains.

m + k = 21
8.50m + 2.75k = 132.50

Use the first equation to solve for k and substitute it into the 2nd equation.

k = 21 - m
8.50m + 2.75(21 - m) = 132.50
8.50m + 57.75 - 2.75m = 132.50
5.75m + 57.75 = 132.50
5.75m = 74.75
m = 13

Prove it
8.50m + 2.75k = 132.50
8.50(13) + 2.75(8) = 132.50
132.50 = 132.50 True

13 coffee mugs

Do you mean conversion factor?