x = number of $10 tickets Sue sold
y = number of $5 tickets Joe sold
joe sold: 2x + y tickets
Sue sold: x + 3y tickets
we need to find 2x+y
(1) x + 3y = 35
cannot get anything. two variables one equation.
(2) gives two equations:
3x + 4y = 70
30x + 20y = 500
solve for x,y and get 2x+y
I was thinking C. But you are correct. Answer has to be (b).
I did not realize that you can form an equation out of the total sales.