Three years ago, the average age of a family of five members was 17 years. A baby having been born, the average age of the family is the same as what was three years ago. The present age of the baby is:

Let the present ages of A, B and C are 3x, 5x and 7x years respectively; then
According to question,
3x + 5x + 7x = 3 x 25
? 15x = 75
? x = 5
Hence, age of A = 3x = 3 x 5 = 15 years

Let the present ages of A and B are 11x and 13x years respectively; then
According to question,
After 7 years the ratio of their ages will be 20 : 23.
(11x + 7 ) / (13x + 7) = 20/23
? (11x + 7 ) 23 = 20 (13x + 7)
? 253x + 161 = 260x + 140
? 7x = 21
? x = 3
Hence, difference of their ages = 13x - 11x = 2x = 2 x 3 = 6 years

Let us assume the present ages of woman and her daughter be 2x and x years respectively ; then
According to question,
The average age of a woman and her daughter is 42 years
(2x + x)/2 = 42
? 3x = 84
? x = 28
Hence, present age of her daughter = 28 years

Let the present ages of Surabhi and Neerja are 6x and 7x years respectively.
According to question,
(6x + 6)/(7x + 6) = 15/17
? (6x + 6)x17 = 15x(7x + 6)
? 102x + 102 = 105x + 90
? 3x = 12
? x = 4
Hence, present ages of Neerja = 7 x 4 = 28 years

Let one year ago the ages of Yamini and Gamini were 6P and 7P years respectively; then
(6P + 5)/(7P + 5) = 7/8
? (6P + 5) x 8 = 7 x (7P + 5)
? 48P + 40 = 49P + 35
? P = 5
Hence, present ago of Gamini = 7P + 1 = 7 x 5 + 1 = 36 years

3 Years age Ritu's age was x years, then
Ritu's present age = x + 3 years
According to question,
Present age of Rahul is 5 years less than Ritu's present age
Hence, present age of Rahul = x + 3 - 5 = x - 2 years

Let us assume the present age of son be x then his father present age will be 3x.
According to question,
Six years hence, the ratio of their ages will be 5 : 2 respectively
(3x + 6)/(x+6) = 5/2
? (3x + 6)2 = 5(x+6)
? 6x + 12 = 5x + 30
? x = 18
Hence, age of Sanyal = 3 x 18 = 54 years

Let the present ages of Namrata and Divya are 4x and 3x years respectively; then
According to question,
4x + 3x = 28
? x = 4
Hence, their present ages are 16 and 12 years.
So required ratio = (16 +4) : (12 + 4) = 20 : 16 = 5 :4

Let the present age of Gopal and Madhawa are 4x and 3x years respectively; then
According to question,
4x + 6 = 26
? 4x = 20
? x = 5
Hence, present age of Madhawa = 3x = 3 x 5 = 15 years

Let us assume 10 years ago, ages of Ram, Shyam and Mohan were 2x, 3x and 4x years respectively.
Present ages of Ram, Shyam and Mohan will be 2x + 10 , 3x + 10 and 4x + 10 years.
According to question,
2x + 10 + 3x + 10 + 4x + 10 = 93
? 9x + 30 = 93
? 9x = 93 - 30
? 9x = 63
? x = 7
The present age of mohan = 4x + 10 = 4x7 + 10 = 38 years