Let present ages of indira and Lizzy are 3k yr and 8k yr, respectively.
∴ 3k + 8 = 20 ⇒ 3k = 12

Correct Option: B

Let present ages of indira and Lizzy are 3k yr and 8k yr, respectively.
∴ 3k + 8 = 20 ⇒ 3k = 12
∴ k = 4
Hence, Lizzy's required age = 8k - 5
= 32 - 5
= 27 yr

Let Sarita;s present age = k yr
Then, Kavita's present age = 2k yr
According to the question,
(2k + 8) / (k + 8) = 22/13

Correct Option: D

Let Sarita;s present age = k yr
Then, Kavita's present age = 2k yr
According to the question,
(2k + 8) / (k + 8) = 22/13
⇒ 26k + 104 = 22k + 176
⇒ 4k = 72
∴ k = 18
Hence, Kavita's age = 2 x 18 = 36 yr

Let 7 yr ago, ages of A and B 4k yr and 5k yr, respectively.
Then, present age of A = 4k + 7
and present age of B = 5k + 7
Now, according to the question,
∴ (4k + 7 + 7) / (5k + 7 + 7) = 5/6

Correct Option: D

Let 7 yr ago, ages of A and B 4k yr and 5k yr, respectively.
Then, present age of A = 4k + 7
and present age of B = 5k + 7
Now, according to the question,
∴ (4k + 7 + 7) / (5k + 7 + 7) = 5/6
⇒ 24k + 84 = 25k + 70
⇒ k = 14
Hence, B's present age = 5 x 14 + 7 = 77 yr

According to the question,
(36 + n) / (50 + n) = 3/4

Correct Option: D

According to the question,
(36 + n) / (50 + n) = 3/4
⇒ 144 + 4n = 150 + 3n
∴ n = 6

Let the ages of A and B are 4N and 5N yr. respectively.
According to the question,
∴ (4N + 4)/(5N + 4) = 14/17

Correct Option: A

Let the ages of A and B are 4N and 5N yr. respectively.
According to the question,
∴ (4N + 4)/(5N + 4) = 14/17
⇒ 68N + 68 = 70N + 56
⇒ 2N = 12
⇒ N = 6
Hence present age of B = 5 x 6 = 30 yr