21 students because if 6 represents 30% u add 6 two more time which equals 18 and 90% then u add 3 more because it is half of 6. when u add 3 more u will get 21 and 100%
65*7=(1+1+1+1+1+1+1)=65+65+65+65+65+65+65=455 she did 65 sit ups every day for one week the expression is right there the answer to solve it is 455. :)