Correct Answer - Option 3 : 17.5 years

**Given: **

The total age of four persons is 86 years

**Formula Used:**

The average age of persons = Sum of ages of Persons/number of persons

**Calculation:**

According to question,

We have to find the average age of persons 4 years ago

Sum of ages of person 4 years ago = 86 - 4 × 4

⇒ 86 - 16

⇒ 70

Now, Average age of four persons = 70/4

⇒ 17.5

**Hence, the average age of four persons 4 years ago was 17.5**