I'm having trouble understanding significant figures. If a problem is requires two equations to finish, which of the original measurements do I use to figure out the significant figure? For ex. 3.001+4.32= 7.321. Then I use this answer for a different equation..for the final answer do I use the measurements for the second eq. or the first measurements?

Answer 1

Both. Determine the number of s.f. for the first operation, then go to the second and determine the number in the final answer. Use 7.32 for the correct number from the first operation.
Here is a good site you can use.
http://www.chemteam.info/SigFigs/SigFigs.html