The pretend element, knoxium, Kx, has the following composition: 164Kx, 164.08 amu (60.44%)
165Kx, 165.11 amu (13.55%)
169Kx, 168.92 amu (%)
What is the average atomic mass of the "knoxium"?

164.08amu
165.48amu
166.04 amu

165.48 amu

Explanation:

First, you need to find the last percentage.

100% = 60.44% + 13.55% + x

100% = 73.99% + x

x = 26.01%

Now, multiply each mass by the respective percentage.

164.08 × 0.6044 = 99.17

165.11 × 0.1355 = 22.37

168.92 × 0.2601 = 43.94

Lastly, add the products together to find the average atomic mass.

99.17 + 22.37 + 43.94 = 165.48

The average atomic mass of "knoxium" is 165.48 amu