Marco and his dad went strawberry picking. Marco's strawberries weighed 10 pounds. If together their strawberries weighed 17 pounds. How much did his dad's strawberries weigh?
1. Marco's strawberries weigh 10 pounds. 
2. Together, Marco and his dad's strawberries weigh 17 pounds. 
3. Therefore, his dad's strawberries weigh 7 pounds.