Pre-Calculus math help!

I have a 100pt. math quiz tomorrow on things that I am not really sure how to do. If anyone could please help me out it would be great. And if you guys could, could you please explain how to do the problems so I could actually learn and not just get the answers.
The first one I am not sure how to do is
1. Convert 4.475 hours into hours, minutes and seconds.
I realize that Hours=4 but i honestly don't remember how to do the rest.
2.Convert 2 miles 3745 feet 10 inches into miles.
The last one is a word problem probably using a graphing calculator. (if you guys can't help with this then it is totally fine)
3. A new fax machine was purchased on january 1st 1998 for a price of $800. After 4 years it was worth $600.
Part A- Algebraically create a linear model that shows the depreciated value of the fax machine.
Part B- Use your model to calculate how much the fax machine will be worth on January 1st 2005.
Part C- Use your model to calculate how much the fax machine will be worth of march 1st, 2001(60th day of the year)
Part D-How many years will it take for the fax machine to become worthless?
Part E- On what date was the Machine worth 599?
Part

all you have to do is know the common conversions such as 60 seconds in a minute and 60 minutes in an hour.
4.475 hours = 4.475 hours
4.475 hours * 60 minutes/1 hour = 268.5 minutes
4.475 hours * 60 minutes/1 hour * 60 seconds / 1 minute = 16110 seconds

same thing with distance. 12 inches in a foot, 5280 feet in a mile.
10in * 1ft/12in * 1mile/5280ft = .000157828283 miles
3745ft * 1mile/5280ft = .70928030303
2miles = 2 miles
add them all up 2+.70928030303+.000157828283 = 2.70943813131 miles

Part A - linear model is just y=mx+b here it is $800 - $50*x = new cost of machine (found because 800-600=200 and 200/4=50

Part B - how many years occur between 1998 and 2005 (7) so $800 - $50*(7) = $450