The sequence ~$a_1, a_2, a_3, a_4, a_5$~is such that ~$a_n = a_{n-1}+ 5$~  for 2 ≤ n ≤ 5. If~$ a_5 = 31$~, what is the value of ~$a_1$~ ?

Stephanie has ~$2\frac{1}{4}$~ cups of milk on hand and makes 2 batches of cookies,using~$\frac{2}{3}$~ cup of milk for each batch of cookies. Which of the following describes the amount of milk remaining after she makes the cookies?

The sum of three integers is 40. The largest integer is 3 times the middle integer, and the smallest integer is 23 less than the largest integer. What is the product of the three integers?

If d = 2.0453 and d* is the decimal obtained by rounding d to the nearest hundredth, what is the value of d*- d ?

Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?

After 4,000 gallons of water were added to a large water tank that was already filled to ~$\frac{3}{4}$~of its capacity, the tank was then at ~$\frac{4}{5}$~ of its capacity. How many gallons of water does the tank hold when filled to capacity?

If a and b are positive integers and ~$(2^a)^b= 2^3$~, what is the value of ~$2^a2^b$~?

If Mel saved more than $10 by purchasing a sweater at a 15 percent discount, what is the smallest amount the original price of the sweater could be, to the nearest dollar?

Members of a social club met to address 280 newsletters.If they addressed ~$\frac{1}{4}$~of the newsletters during the first hour and~$\frac{2}{5}$~ of the remaining newsletters during the second hour, how many newsletters did they address during the second hour?