Answer :

in one ounce there are 28.3495 grams 
                      rounded  28.25 grams
so in 21 grams there are 0.7407532009 ounces
                      rounded to  3/4 = .75
  there are 3/4 of an ounce in 21 grams
28.25 g per ounce

21 grams divided by 28.25

answer= 0.74