i'm confused with your question, first of all it seems that your statement is missing a little details, like how many dogs she's walking? but if that's not the case and your teacher tells you that you can put any number of dogs then here's the equation.
a-number of dogs
b-number of how much she earns
c-number of times she does this
3×5×2=30 -jane earns 30 dollars just by walking 3 dogs on the weekends.
25% of plastic utensils are knives.
I think answer should be 20
1. x = 0, y = 4
2. x = -3, y = -5
1. Substitute x by 4 - y
Now you have 2y + 4 = 12
Solve for y and you have y = 4
Substitute y and you have x = 0.
2. Substitute y by x - 2
Then you get 2x - 3(x-2) = 9 [Note: Distribute the negative sign]
After distributing you get -x + 6 = 9
Solve for x and you get x = -3 (Multiply -1 on both sides)
Substitute x now and y = -5
Hope this helps.