Jordan has a jar of quarters. When he has 60 quarters in the jar, the jar weighs 52 ounces. When there are 125 quarters in the jar, the jar weighs 65 ounces. What is the weight of the empty jar?

60q+j=52

125q+j=65

multiply first equation by - 1 and add to 2nd

-60q-j=-52

125q+j=65 +

65q+0j=13

65q=13

divde both sides by 65

q=0.2oz

sub back

when

60q+j=52

60 (0.2) + j=52

12+j=52

minus 12 both sides

j=40

the jar is 40 ounces