Alvin pays for 4 brownies and 3 cookies. Milly spends twice as much paying for 2 brownies and 16 cookies. A brownie is how many times as expensive as a cookie?
We let x be the cost of a brownie and y the cost of a cookie.
Alvin pays 4x+3y. Milly pays 2x+16y.
Since Milly pays twice as much as Alvin we form an equation.
So a brownie is 5/3 times as expensive as a cookie.