6divide into 22 its hw my teacher said if i don’t get it right everyone in my class will not have lunch but like in the classroom not in the cafeteria

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?