So for a better presentation: https://i.sstatic.net/HCzft.jpg
I need to prove this using mathematical induction, so i started with a base of $n=1$
Since $i$ starts at $i = 1$ I got this:
$$\frac{1}{i(i+1)} = \frac{n}{n+1}$$ $$\frac{1}{2} = \frac{1}{2}$$
So since this was true I went to the induction part: I chose $n = k$ and assumed this was true:
$$\frac{1}{i(i+1)} = \frac{n}{n+1}$$ $$\frac{1}{i(i+1)} = \frac{k}{k+1}$$
but I got stuck here since I didn't know if I needed to increment $i$ or not and because I didn't know if I needed to add the summation symbol or not and needed to do a few things with it.