I assume you're trying to find either the amount of students that came or the amount from the beginning of the year. In order to do this 651*0.05= 32.55 (the amount of students that came(round it up)) To find the amount of students at the beginning of the year 651-32.55= 618.45 which would round down to 618. There were 33 students that came and 618 at the begging of the year.
651*0.05=32.55 651-32.55=618.45
