Q: Austin and Jake start descending from the 9th floor of a building at the same time. Austin uses the elevator and Jake uses the stairs, descending 3 steps every second. The stairs have 30 steps across each floor. If the elevator will take a minute to get to ground level, how many seconds later will Jake get to the ground floor?
A: Jake has to descend 30 steps on 9 floors for a total of 9 * 30 = 270 steps. He descends 3 steps every second so he will descend 270 steps in 270 / 3 = 90 seconds. Austin will get down after only a minute (60 seconds) so Jake will get down 90 - 60 = 30 seconds later. The answer is 30.

Q: Roxanne bought 2 cups of lemonade for $2 each and 2 sandwiches for $2.50 each. How much change must she get from a $20 bill?
A: Two cups of lemonade amount to $2 x 2 = $4. Two sandwiches amount to $2.50 x 2 = $5. So, the total amount that Roxanne had to pay was $4 + $5 = $9. Thus, her change must be $20 - $9 = $11. The answer is 11.

Q: Kevin is a fruit vendor. He always sells a total of 50 crates of fruit per week. Last week he sold 13 crates of grapes, 20 crates of mangoes, and the rest were passion fruits. How many passion fruit crates did he sell?
A:
Between grapes and mangoes, we have 13 + 20 = 33 crates. The remaining crates are passion fruits, so we have 50 - 33 = 17 crates of passion fruit. The answer is 17.