Algebra
# Linear Equations

Let $f(x)$ be a linear function. Given $f(6)-f(2)=12$ find the value of $f(12)-f(2)$.

Three identical small hoses can fill the swimming pool in 5 hours (working together).

Using two large hoses and one small hose, how much time will it take to fill the swimming pool? Give your answer in minutes.

The battery of a cell phone is enough for 9 hours when the phone is off and 1.5 hours when the phone is on.

If the battery of my fully charged phone was discharged in 8 hours, then how long did I have it on?

Assume that every week has 7 days, every month has 4 weeks, and every year has 12 months.

The age of my grandson in days is numerically equal to the age of my son in weeks. The age of my grandson in months is numerically equal to my age in years. The sum of ages of my grandson, my son, and me is 120 years. What is my age in years?