Isabelle gets a job so she can save enough money to go to a concert with her two brothers. Her ticket costs $20. Her brothers both get the children's discount, and each of their tickets cost $10. Her brothers have saved $5 between the two of them and Isabelle has saved $5. If her job pays $3 per week, how many weeks must she work to afford the tickets? Think carefully first, then make a decision:
The tickets for both of her brothers will cost her $10 * 2 = $20. To buy tickets for all of them, it will cost Isabelle $20 + $20 = $40. Between all of them, they have saved a total of $5 + $5 = $10. Since they have already saved $10, she needs to earn an additional $40 - $10 = $30 to afford the tickets. Since she makes $3 per week, it will take her $30 / ($3 / week) = 10 weeks to save enough money for all of the tickets. So, the answer is 10.