I was wondering if someone could help me with some math problems for my environmental science class (sorry in advance if this is in the wrong forum).

I'm not sure how to set up the problems, but the calculations are fine (although we are not allowed to use calculators when we do these problems). Here are the problems:

A typical TV uses 40 watts of electricity when turned off. There are ~250 mil. TVs in the US.
A pound of coal contains 14000 BTUs.
Complete combustion of a pound of coal produces 2.5 lb. of CO2.
One kWh = 3400 BTUs.

Calculate the number of kWh used annually in the US. (answer: 8.75*10^10)
Calculate the number of tons of coal required annually to provide electricity. (answer: 1.1*10^7)
Calculate the number of CO2 emissions produced annually. (answer: 2.7*10^7)

Thanks in advance