I have no idea how to do these:

A) "Find the sum of the arithmetic series"

http://www.freewebs.com/smaii/sigma.bmp

B) "Expand (x+2)^4"

So far, all I could manage to get is 1x^4(2)^0+4/1x^3(3). Is there an easier way to do this question without it becoming so messy/confusing?

Thanks in advance!