Some sums questions again:

Have some thoughts about if these solutions are correct..all comments highly appreciated

First one out is:

Write without Sigma notation

well here is my shot should be:

Don't understand this one: you wrote the first three summands of the above series...so?
Then we have a "calc the sum of stuff":

well I figured since there is a 4 between each term why dont we:

This is the sum of an arithmetic series with first element 3 and common difference 4. If is an arithmetic series, with common difference , then the sum of its first consecutive n terms is .
We have another question: calculate the sum of:

well if I write it so the first number overlapswith the last

1+ .............3+ ...........5...........+(2n-1)

(2n-1)+1 +(2(n-1))+3 + (2(n-2))+5 + (2n-1)+1

then

Correct. Again, this is the sum of an arithmetic series with difference 2 and first element 1
Then a more difficult one calculate the sum of:

hey lets divide by a

oohh look divide by (1-k)

hej lets add

turned out like this.