Ascientist puts 45.5 grams of material into a jar she then removes 8.225 grams of the material how much of the material remains in the jar

This is a  subtraction problem. The word 'removes' strongly shows this. SO you equation is 45.5-8.225. With subtraction you have to line your digits and put zeroes on the first number so it can match/add up. 

After your done with subtraction you should get  37.575