Answer:
11y is the exact value.
Step-by-step explanation:

let the solution be 
let the solutions be a = 3, b = 1
is the equation with consistent value.
To solve this answer, you are trying to find 55% of 600, because that is the number of people who chose plastic bag.
55% can be re-written as 55/100 OR 0.55 since percentages are always out of 100.
So, we do 0.55*600, which gives us 330. 330 people carry plastic bags.