[Question]John buys 2 packs of index cards for all his students. He has 6 classes and 30 students in each class. How many packs did he buy?
[Answer]John has 6 * 30 = 180 students. So he bought 180 * 2 = 360 packs. The answer is 360.

[Question]Mrs. Garcia pays her insurance quarterly at $378. How much does she pay in a year for her insurance?
[Answer]Since there are three months in a quarter, then there are 12 / 3 = 4 quarters in a year. So, Mrs. Garcia pays $378 x 4 = $1512 in a year for her insurance. The answer is 1512.

[Question]A crayon factory makes 4 colors of crayons. They put 2 of each color crayon in each box. The factory produces enough crayons to fill 5 boxes per hour. How many crayons does the factory produce in 4 hours?
[Answer]Each box contains 4 * 2 = 8 crayons. In an hour, they make 8 * 5 = 40 crayons. In 4 hours they make 4 * 40 = 160 crayons. The answer is 160.

[Question]Sarah's age is equal to three times Mark's age minus 4. Mark is four years older than Billy. Billy is half Ana's age. If Ana will be 15 in 3 years, how old is Sarah?
[Answer]
First figure out how old Ana is right now by subtracting 3 from 15: 15 - 3 = 12. Next, figure out how old Billy is by dividing Ana's age by 2: 12 / 2 = 6. Now figure out how old Mark is by adding 4 to Billy's age: 6 + 4 = 10. Now, to figure out Sarah's age, first multiply Mark's age by 3: 10 * 3 = 30. Finally, subtract 4 from triple Mark's age to find Sarah's age: 30 - 4 = 26. The answer is 26.