What is the correct equation for calculating the average atomic mass for 3 isotopes? (pls be 100%of your answer pls no guessing)
add all the masses together and divide by 3
add all the protons together and divide by three
multiply the percent abundance by each mass, add them up, and then divide by 3 multiply the percent abudance by each mass and add them up

The correct equation for measuring the average microscopic weight  for 3 isotopes is multiply the rate of abundance by each weight and add them.

Explanation:

To calculate the average microscopic mass of element using weights and relative abundance we have to follow the following steps.

Take the correct weight of each isotope (that will be in decimal form)Multiply the weight of each isotope by its abundanceAdd each of the results together.

This gives the required  average microscopic weight of the three isotopes.

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -

Ithink it is letter b, i may be wrong but i think that is the answer