3/56 is the fraction of the bag of marble that each person receive.
bag of marbles = 3/8
divided by = 7 people
3/8 ÷ 7
In dividing fraction, get the reciprocal of the 2nd fraction and multiply it to the 1st fraction.
1st fraction = 3/8
2nd fraction = 7 ⇒ 7/1 , reciprocal = 1/7
3/8 * 1/7 = 3 * 1 / 8 * 7 = 3/56
each person will receive 3/56 of the bag of marbles.