Ruel has a total of 4 x 10 = 40 stamps from the four books. He also has 6 x 15 = 90 stamps from the six books. Therefore, he has a total of 40 + 90 = 130 stamps.
The answer: 130
Reverse engineering the question: Ruel has four books of 10 stamps and six books of 15 stamps. How many stamps does Ruel have?

Each plastic chair costs $55 / 5 = $11. Two chairs cost $11 x 2 = $22. A portable table costs $11 x 3 = $33. Manny has to pay a total of $22 + $33 = $55. Thus, Manny will be left with $100 - $55 = $45.
The answer: 45
Reverse engineering the question: Three plastic chairs cost as much as a portable table. Five plastic chairs cost $55. If Manny wants to buy one portable table and two chairs, how much will be left in his $100?

Mrs. Lopez needs to buy two adult tickets for $11 x 2 = $22. She needs to buy two senior citizen tickets for $9 x 2 = $18. She needs to buy three children’s tickets for $8 x 3 = $24. For everyone’s tickets, Mrs. Lopez needs to spend $22 + $18 + $24 = $64 for seven tickets.
The answer: 64
Reverse engineering the question: Mrs. Lopez and her family are going to the movie theatre. Adult tickets are $11. Children’s tickets (ages 3-12) are $8. Senior citizen’s tickets (ages 60+) are $9. Mrs. Lopez needs to buy movie tickets for her husband, herself, her parents (ages 72 and 75), and her three children (ages 7, 10, 14). How much money does she need to buy everyone’s tickets?

For the fourth - grade classes, Jessa needs 3 classes * 30 cupcakes / class = 90 cupcakes. Adding the cupcakes for the P.E. class 50, she needs to make a total of 90 cupcakes + 50 cupcakes = 140 cupcakes.
The answer: 140
Reverse engineering the question:
Jessa needs to make cupcakes for 3 fourth-grade classes that each have 30 students and a P.E. class with 50 students. How many cupcakes does she need to make?