We have a question: Alyssa took 100 photos on vacation. She wants to put them in a photo album with 30 pages. She can place 3 photos each on the first 10 pages. Then she can place 4 photos each on the next 10 pages. If she wants to put an equal number of photos on each of the remaining pages of the album, how many photos can she place on each page?
And an answer: 3
So how you got the answer?
There are 3 x 10 = 30 photos in total that can be placed in the first 10 pages. There are 4 x 10 = 40 photos in total that can be placed in the next 10 pages. A total of 10 + 10 = 20 pages of the album have been used. A total of 30 + 40 = 70 photos can be placed on those 20 pages. So there are still 100 - 70 = 30 photos left to be placed on the album. And there are 30 - 20 = 10 pages left in the album. Therefore, 30 / 10 = 3 photos can be placed on each of the pages.

We have a question: A fan can create an airflow of 10 liters per second. If the fan works for 10 minutes each day, calculate the amount of airflow it will create in one week.
And an answer: 42000
So how you got the answer?
If the fan works for 10 minutes each day, in a week with 7 days, it will have worked for 10 * 7 = 70 minutes. Since a minute has 60 seconds, the total time in seconds that the fan will have worked in one week is 70 * 60 = 4200 seconds. Since the fan can create an airflow of 10 liters per second, in 4200 seconds, it will create an airflow of 4200 * 10 = 42000 liters.

We have a question: The girl scouts earned $30 total from selling delicious cookies. They want to go to the pool. It will cost them $2.50 per person to go and 10 people are going. What is the amount left?
And an answer: 5
So how you got the answer?
The girls paid $2.50 / person * 10 people = $25. The girls have $30 - $25 = $5 left.