She gives the boy she likes 10 stickers. After giving the boy his stickers, she has 100 10 = 90 stickers left. She gives her best friends 90 / 2 = 45 stickers. This leaves Clara with 90 45 stickers = 45 stickers.
The answer: 45
Reverse engineering the question: Clara brings a package of 100 stickers to school. She gives 10 stickers to a boy she likes. She gives half of the stickers which she has left to her best friends. How many stickers does Clara have left?

60 packs of cards * 7 cards per pack = 420 cards. 420 cards / 10 cards per page = 42 pages.
The answer: 42
Reverse engineering the question: Punger collects baseball cards. He buys 60 packs of baseball cards. Each pack has 7 cards inside. He wants to put these cards in special pages to protect the cards. Each page can hold 10 cards. How many pages does he need to buy?

The band played 5 + 7 = 12 songs in their first two sets. They have 30 - 12 = 18 songs left for the third set, fourth set and encore. Since they played 2 songs in the encore, they have 18 - 2 = 16 songs to play on the third and fourth sets. They will play 16 / 2 = 8 songs on average over the third and fourth sets.
The answer: 8
Reverse engineering the question: The school band has 30 songs in their repertoire. The band played 5 songs in their first set and 7 in their second set. The band will play 2 songs for their encore. Assuming the band plays through their entire repertoire, how many songs will they play on average in the third and fourth sets?

James earns 20 * .2 = $4 less while working his second job. So he earns 20 - 4 = $16 an hour. At his first job he earns 20 * 30 = $600. He works 30 / 2 = 15 hours at his second job. So he earns 15 * 16 = $240. So he earns 600 + 240 = $840 a week.
The answer: 840
Reverse engineering the question:
James earns $20 an hour while working at his main job. He earns 20% less while working his second job. He works 30 hours at his main job and half that much at his second job. How much does he earn per week?