Y = 3bx - 7x
y = x(3b - 7)
Divide each side by 3b - 7 (assume that it is not zero).

Answer:
The purple crayons take up 1/4 of the crayons in the jar. To get the answer:
140/4 = 35
I believe the answer is the 64 ounce container that is $3.20. the unit price of it was 0.05 while the other one was 0.055