Question

I dont understand how to find the relative atomic mass please help

Answer 1

Ever heard of isotopes?
If not look it fast up on the wiki.
Else continue reading:

The relative atomic mass is the mass of that elemental where we take into account that natural isotopes exist of that elemental which could be for example integrated into a molecule of interest in a sample. So to get the relative atomic mass we take product of the mass of the isotope and it's relative natural appearance:
\[m _{relative}=\Large \sum_{i=1}^{N}p _{i}m_{i}\]

Answer 2

Very straight forward.

Answer 3

If you still don't understand, you can click on the link to see an example along with the explanations. https://www.youtube.com/watch?v=SdhLTfma_Eg