In 2015, there were about 22 million teenagers (aged 13-17) in the United States. They each sent an average per month. About how many messages did all of teenagers in the United States send each month? Express your answer using scientific notation

The sum of the first eight terms of an arithmetic progression is 9m + 14. the fifth term of the06 progression is 2m - 6, where m is a constant. given that the first term of the progression is 26,find the value of the common difference, d and thevalue of m.

How many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.) how many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.)

Ahealth-food producer has 250 samples of a new snack to distribute in the mall. the producer has to keep at least 50 samples for display in the health food for the product launch. how long will the samples last if consumers are taking the samples at a rate of 25 every hour