[Question]: 40 less than 10 times Diaz's age is 20 more than 10 times Sierra's age. If Sierra is currently 30 years old, how old will Diaz be 20 years from now?
[Answer]: If Sierra is currently 30 years old, 10 times her age is 30 * 10 = 300. Twenty more than 10 times Sierra's age is 300 + 20 = 320. 320 is 40 less than ten times Diaz's age so 10 times Diaz's age is 320 + 40 = 360. If ten times Diaz's age is 360, Diaz is 360 / 10 = 36 years old. Twenty years from now, Diaz will be 20 + 36 = 56 years old.
So the answer is 56.

[Question]: Randy has $200 in his piggy bank. He spends 2 dollars every time he goes to the store. He makes 4 trips to the store every month. How much money, in dollars, will be in his piggy bank after a year?
[Answer]: Randy spends 2 * 4 = 8 dollars every month. Randy spends 8 * 12 = 96 dollars in a year. Randy will have 200 - 96 = 104 dollars in his piggy bank after a year.
So the answer is 104.

[Question]: Jill can run up a hill at 9 feet/second and down a hill at 12 feet/second. How long does it take her to run up and down a 900 foot hill?
[Answer]:
First find the time it takes Jill to run up the hill: 900 feet / 9 feet / second = 100 seconds. Then find the time it takes Jill to run down the hill: 900 feet / 12 feet / second = 75 seconds. Then add the two times to find Jill's total time: 100 seconds + 75 seconds = 175 seconds.
So the answer is 175.