9=7+a
a+8=b+5
Use both equations to work out the value of b

The administrator of a large assisted living facility wanted to know the average age of the residents living at the facility. he randomly selected 12 residents and determined their age, listed here: 80, 65, 75, 83, 68, 73, 88, 79, 94, 72, 79, 68 what's the average age of the sample of residents? a. 79 years old b. 68 years old c. 75 years old d. 77 years old

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

At noon a tank contained 10cm water. after several hours it contained 7cm of water. what is the percent decrease of water in the tank?