There are three isotopes of X element (X): X-17 isotope: atomic mass17.2 amu, abundance:78.99%
X-18isotope: atomic mass 18.1 amu, abundance 10.00%
X-19isotope: atomic mass:19.1 amu, abundance: 11.01%
Calculate the average atomic mass of X.

r just means there's a number of carbon in teh chain. for example rcooh means that after x number of carbon, the chain ends with cooh.

explanation:

you did not give any options thus this is the best answer i can give to you with this little information you have given

> they are both natural and not man made

> they can be tracked and predicted by the right tools

-love shrooms

diaria maybe go see a doctor about that