Lets use the letter C to represent cats and D to represent dogs.
A) 2.35c + 5.50d = 89.50
For B, they give you numbers to plug into your equation.
c = 8
d= 14
B) 2.35(8) + 5.50(14) = 89.50
18.80 + 77.00 = 95.80
So what Pat said is incorrect because that would mean they spent more than 89.50.
Hope this helps! :)