It seems that you have missed the necessary options for us to answer this question, but anyway here is the answer. William adds two values, following the rules for using significant figures in computations. He should write the sum of these two numbers by using the same number of decimal places as the least precise value. Hope this helps.
Answer :
The pressure of carbon dioxide in the atmosphere in mmHg is 0.239mmHg.
The pressure of carbon dioxide in the atmosphere in atm is
.
Explanation :
The conversion used for pressure from torr to mmHg is:
1 torr = 1 mmHg
The conversion used pressure from torr to atm is:
1 atm = 760 torr
or,

As we are given the pressure of carbon dioxide in the atmosphere 0.239 torr. Now we have to determine the pressure of carbon dioxide in the atmosphere in mmHg and atm.
<u>Pressure in mmHg :</u>
As, 
So, 
Thus, the pressure of carbon dioxide in the atmosphere in mmHg is 0.239mmHg.
<u>Pressure in atm:</u>
As, 
So, 
Thus, the pressure of carbon dioxide in the atmosphere in atm is
.
2.22 g of NaF*1mol/41.97g of NaF =0.0529 moles