To find the total amount Mrs. Johnson gave away, you need to know how much she gave the son. Because the ratio of the money given is 5:6, the amount of money he received has to be 5/6 of the money the daughter received.
So, the son received 5/6 of 2400.
To find this, multiply 5/6 x 2400 to get 2000.
The daughter received 2400 and the son received 2000, so the total amount Mrs. Johnson gave away is 4400 dollars.
Unit fractions are fractions with a 1 as the numerator(number on top)
so 3/8 equals 1/8+1/8+1/8