Reverse Thinking( Week 2 Practice) 1. When 15 is added to a certain number, the answer is 31. What is the number? 2. 21 plus a certain number is 118. What is the number? 3. Jane is 15 years old, which is equal to half of David's age of next year. What is the age of David now? 4. There were 55 books in a bookshelf originally. After half of the storybooks were borrowed by students, 30 books were left in the shelf. How many storybooks were there originally? 5. A Number X is added to 6 and the result is then reduced by 9. The final result is 7. What is the number X? |