Dana wants to make two types of dog treats. she has 10 cups of peanut butter and 12 cups of flour. her dog bone treat recipe uses 3 cups of peanut butter and 2 cups of flour to make one tray. a tray of her oatmeal dog treat recipe uses 1 cup of peanut butter and 4 cups of flour. she plans to sell trays of dog treats at the town festival and charge $6 for a tray of dog bone treats and $7 for a tray of oatmeal treats. dana wants to maximize her income from selling the dog treats.

There are missing info. I encountered this problem before. The missing info was:
when writing constraints for the problem, what is the most reasonable definition for the variables x and y?

Here was my
constraints: 
10 cups of peanut butter ⇒ x < 10
12 cups of flour ⇒ y < 12

dog bone treat : 3x + 2y ; price : 6 per tray
oatmeal dog treat : x + 4y ; price : 7 per tray

dog bone treat: 3(3x + 2y) = 9x + 6y
oatmeal dog treat: 1(x+4y) =  x + 4y
                                                  10y+ 10y

3 x 6 =18
1 x 7 =  7
            25

variable x is the peanut butter. It should not exceed the 10 cups of peanut butter.
variable y is the flour. It should not exceed the 12 cups of flour.