They give us the weight of carbon dioxide that removes 1 acre of algae. To determine moles we are going to convert the weight from tons to grams and then divide it by the molar mass of carbon dioxide.
We take in count following:
1ton=1x10^6g
1molCO2=44.01g
1year=365days
So, the moles that 1 acre of algae removes in a year will be:
Answer: In a year, are removed 2.2 x10^7 moles of carbon dioxide