Simplify: (−7a − 19c) − (−12a + 30c) − (−21a − 11c)

Scrub a dub toothbrushes are $4.00 each. there is a 10% discount, but there is also a 6% sales tax after the discount is applied. what is the new price after tax? round to the nearest penny

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?

Determine if the outside temperature is a function of the time of day or if the time of day is a function of temperature and explain why or why not.