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.

Average atomic mass = 17.5 amu.

Explanation:

Given data:

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%

Average atomic mass of X = ?

Solution:

Average atomic mass  = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass) + (abundance of 3rd isotope × its atomic mass)  / 100

Average atomic mass  = (78.99×17.2)+(10.00×18.1) +(11.01+ 19.1) /100

Average atomic mass =  1358.628 + 181 +210.291 / 100

Average atomic mass  = 1749.919 / 100

Average atomic mass = 17.5 amu.