Interpreting Expressions Breanna thought of a number, added 5 to it, and then multiplied her answer by 3. She got a final number of 21. What was her starting number?

3. solve the given inequality and graph the solution on a number line.

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

Prove that the value of the expression 7^8–7^7+7^6 is divisible by 43.