Betty is 60 years old, and she is the oldest person in the family. Her daughter is 40 percent younger than she is, and her granddaughter is one-third her mother's age. How old is the granddaughter?
Let's think: Betty's daughter is 40 / 100 * 60 = 24 years younger than she is. That means her daughter is 60 - 24 = 36 years old. So the granddaughter is 1 / 3 * 36 = 12 years old.. The answer is: 12.

Oscar wants to train for a marathon. He plans to add 2/3 of a mile each week until he reaches a 20-mile run. How many weeks before the marathon should he start training if he has already run 2 miles?
Let's think: Oscar needs to increase his maximum running time from 20 - 2 = 18 miles. Oscar will need a total of 18 / ( 2 / 3 ) = 27 weeks to prepare.. The answer is: 27.

Josh has 18 yards of ribbon that is to be used equally to 6 gifts. If each gift will use 2 yards of ribbon, how many yards of ribbon will be left?
Let's think: The 6 gifts will use 6 x 2 = 12 yards of ribbon. So, 18 - 12 = 6 yards of ribbon will be left.. The answer is: 6.

The perimeter of a square-shaped piece of paper is 20 cm shorter than the height of a computer screen. How many cm is the height of the screen if the side of the square paper is 20 cm?
Let's think:
The perimeter of a square is found by 4 * side, which means the square paper has a perimeter of 4 * 20 = 80. Since the perimeter of the square is 20 cm shorter than the height of the computer screen, the height of the computer screen is 20 + 80 = 100cm.. The answer is: 100.