Hadley loves to do volunteer work at the local library. On a certain day, she neatly arranges 100 books on the shelf. By lunchtime, a certain number of books had been borrowed. She added 40 more books to the same shelf. By evening, 30 more books had been borrowed. If the shelf had 60 books remaining by the evening, how many books had been borrowed by lunchtime? Give the rationale and then the answer.
Let's think step by step. Let x be the number of books borrowed by lunchtime. So by lunchtime, the remaining number of books will be 100 - x. After adding 40 more books, the total number of books increased to 100 - x + 40. By evening, after 30 more books have been borrowed, the total number of books remaining is 100 - x + 40 - 30 = 60. Thus 110 - x = 60. Thus x = 50 books.. The answer is: 50.

A fast-food chain offers free delivery for a minimum purchase of $18. Danny ordered 2 quarter-pounder burgers for $3.20 each, 2 large fries that cost $1.90 each, and 2 milkshakes that cost $2.40 each. How much more worth of food should he order to avail of the free delivery? Give the rationale and then the answer.
Let's think step by step. Two quarter - pounder burgers cost $3.20 x 2 = $6.40. Two large fries cost $1.90 x 2 = $3.80. Two milkshakes cost $2.40 x 2 = $4.80. The total amount spent for the burgers, fries, and shakes is $6.40 + $3.80 + $4.80 = $15. Therefore, he should order $18 - $15 = $3 worth of additional food to take advantage of the free food delivery.. The answer is: 3.

When Jayson is 10 his dad is four times his age and his mom is 2 years younger than his dad. How old was Jayson's mom when he was born? Give the rationale and then the answer.
Let's think step by step. When Jayson is 10 his dad is 10 x 4 = 40 years old. His mom is 40 - 2 = 38 years old. When Jayson is born, his mom is 38 - 10 = 28 years old.. The answer is: 28.