A car rental charge is $100 plus $0.30 per mile traveled. Determine the equation of the line that represents the cost by the number of miles traveled.
y = 100 + 0.3x
After 2 minutes on a treadmill, Jenny has a heart rate of 82. After 3 minutes she has a heart rate of 86. Assuming that Jenny's heart rate H is a linear function of the time T on the treadmill, write H as a linear function of T.
H = 4T + 74
A company can make a total of 20 solar heaters for $13,900, while 10 heaters cost $7500. Write a linear equation for the total cost as a function of the number of heaters produced.