We have the following expression given:

We can start selecting as common factor 4y^2 and we got:

Now we can select y+7 as common factor and we got:

So then our final answer would be:
Think of this situation as a system of equations.
let y be the price of hotdogs
let x be the price of hamburgers
5y + 2x = 8
2y + 5x = 9.50
now use your solution method of choice
substitution, elimination, matrices, etc
Answer:
72 marbles are yellow
Step-by-step explanation:
You can work this out by rearranging the equation and isolating the x.
4x + 12 = 36
4x = 36 - 12 (I moved the +12 to the other side, which means it becomes -12)
4x = 24 (36 - 12 = 24)
x = 24 / 4 (You need to isolate the x, and because it was being multiplied by 4, I divided both sides by 4 to leave me with just x)
x = 6 (24 divided by 4 is 6).