Answer:
28.1
Explanation:
Divide the percentage abundances by 100:
92.2% ÷ 100 = 0.922
4.7% ÷ 100 = 0.047
3.1% ÷ 100 = 0.031
multiply them by their corresponding mass number:
0.922×28 = 25.816
0.047×29 = 1.363
0.031×30 = 0.93
add them all together to get your final answer:
25.816 + 1.363 + 0.93 = 28.109
to one decimal place:
28.1
I hope that helps!!!
