SOLUTION: What is the value of the expression 2(n upper) sigma 1(i lower bound) 3i= a)12 b)9 c)6 d)3 Can someone help me please? I do not "get" it!

I'm guessing that means this:

.  If not post again. 
  


Then this means to plug in all the integers for i into 3i,
starting with what i is equal to on the bottom and ending
with i = whatever the value on the top is.  Then add up
the results.

So, on the bottom we see that we start with i=1, so we
substitute i=1 into 3i and get 3(1) or 3

The next integer after 1 is 2, so we substitute i=2 into
3i and we get 3(2) = 6.

We've finished substituting because the number on the top
is 2 and that means we stop already.  Usually there is 
bigger number than just 2 on top, but that's all there
is here so we now add up what we've gotten:

3 + 6 = 9, so the correct answer is (b).

Edwin