Q: Ben's hockey team is 60% boys and the rest are girls. Half the girls are juniors and the other half are seniors. If the team has 50 players, how many junior girls are there?
A: 10
Step-by-step reasoning process: The team is 40% girls because 100 - 60 = 40. The team has 20 girls because 50 x .4 = 20. The team has 10 junior girls because 20 / 2 = 10.

Q: Julieta went to the store to buy a backpack and three ring-binders for her school supplies. She knew the backpack was $50, and each ring-binder cost was $20. However, at the store, she found out that the price of a back had increased by $5, and the price of a ring-binder had reduced by $2. Calculate the total amount of money Julieta spent at the store.
A: 109
Step-by-step reasoning process: Initially, a backpack cost was $50; when it increased by $5, the price became $50 + $5 = $55. The price of a ring - binder $20, when it reduced by $2, the price became $20 - $2 = $18. If she wanted to buy 3 ring - binders, she spent $18 * 3 = $54. In total, Julieta spent $55 + $54 = $109.

Q: I bought a pair of shoes for $51. The shoes were already marked 75% off. What is the original price of the shoes?
A: 204
Step-by-step reasoning process: Let X be the original price of the shoes. The discounted price is X - X * 75% = 0.25 * X = $51. The original price of the shirt was X = $51 * 4 = $204.

Q: A certain tree was 100 meters tall at the end of 2017. It will grow 10% more than its previous height each year. How long has the tree grown from 2017 until the end of 2019?
A: 21
Step-by-step reasoning process: At the end of 2018, the tree will grow 100 x 10 / 100 = 10 meters more. Thus, its height at the end of 2018 is 100 + 10 = 110 meters. At the end of 2019, the tree will grow 110 x 10 / 100 = 11 meters more. So, its height at the end of 2019 is 110 + 11 = 121 meters. Therefore, the tree has grown 121 - 100 = 21 meters.