The present ages of three persons are in the proportion 4 : 5 : 7. Seven years ago, the sum of their ages was 59 years. The present age of youngest of them is

The youngest is 20 years old now.

Let the present ages be 4x, 5x and 7x, summing to 16x.

Seven years ago each was 7 less, so the sum was 16x - 21.

This equals 59 : 16x - 21 = 59, so 16x = 80.

Thus x = 5 and the youngest = 4x = 20 years.