Mike bought 16 paperback books at the used book store for $10.95. Some cost $0.60 and some cost $0.75. How many of each did he buy?

X=number of books that cost 0.60

y=number of books that cost 0.75

x+y=16

0.6x+0.75y=10.95

solve

multiply second equation by 10 for nicity

6x+7.5y=109.5

multiply first equesiotn by - 6 and add to second

-6x-6y=-96

6x+7.5y=109.5 +

0x+1.5y=13.5

1.5y=13.5

divide both sides by 1.5

y=9

sub back

x+y=16

x+9=16

minus 6

x=7

seven 0.60 books and nine 0.75 books