Sarah is 50 years old and Nazrul is 40 years old. How long ago was the ratio of their ages 3 : 2?

Question: Sarah is 50 years old and Nazrul is 40 years old. How long ago was the ratio of their ages 3 : 2?

Solution:
Let us assume x years ago
At present: Sarah is 50 years and Nazrul is 40 years
x years ago: Sarah’s age = (50 - x) and Nazrul's age = (40 - x)

ATQ,
(50 - x)/(40 - x) = 3/2
⇒ 100 - 2x = 120 - 3x
⇒ x = 20

Therefore, the answer is 20 years.