Elizabeth and Lauren sold cookies for a school fundraiser and made $1,316.70. Together the girls sold a total of 831 cookies. Elizabeth sold chocolate chip cookies for $1.50 each, and Lauren sold peanut butter cookies for $1.65 each. How many cookies did Lauren sell?

Question

How would I set this up in order to solve for each?

Answer 1

If they sold x chocolate chips, then
the rest (831-x) were peanut butters
Now just add up the amounts made on each kind.
1.50x + 1.65(831-x) = 1316.70