a. (2x + 6) - 4 represents how to find the area of the table cloth. (to be honest, I'm not sure why you have to subtract the lace, or what I'm assuming is the lace...)
b. 2x + 6 represents how to find the area of the table cloth.
c. 2x represents the x length getting multiplied by 2, since there are 2 sides.
I hope this helps just a little bit though. I'm sorry I could get part a very well.