An animal shelter spends $3.50 per day to care for each bird and $4.00 per day to care for each cat. Katherine noticed that the shelter spent $103.50 caring for birds and cats on Friday. Katherine found a record showing that there were a total of 28 birds and cats on Friday. How many birds were at the shelter on Friday?
No. of birds X
No. of cats 28 - X
103.50 = 3.50X + 4.00(28 - X) = 3.5X + 4x28 - 4X = 3.5X + 112 - 4X
O.5X = 112 - 103.5 = 8.5
X = 17
No. of birds 17
No. of cats 28 - X + 28 - 17 = 11
Check: $3.5 x 17 + $4 x 11 = $59.5 + $44 = $103.50