2x can represent the starting cost for a cookie.
5 can represent what goes to the boy scouts.
13 means the total amount of money you are paying.
Question:
Boy scouts sell cookies for x dollars. It costs $2 to start because that is labor of making the cookie. In addition to that, you need to pay $5 so it can go to supporting them. In total, you pay $13. How much money did you pay for cookies?
Solution:
2x + 5 = 12
~Subtract 5 to both sides
2x = 7
~Divide 2 to both sides
x = 3.5
Therefore, the cookie cost $3.50 each.
Best of Luck!