A father tells his son, "I was of your present age when you were born." If the father is now 36 years of age, how old was the boy 5 years ago?

Options

A. 13
B. 15
C. 17
D. 20

Explanation

To solve the problem step by step, we can follow these instructions:

1. **Understand the relationship between the father and son's ages**: The father states that he was the same age as the son is now when the son was born.

2. **Define the variables**:
- Let the current age of the son be \( x \).
- Since the father is currently 36 years old, we can express the father's age when the son was born as \( 36 - x \).

3. **Set up the equation**: According to the father's statement, when the son was born, the father's age was equal to the son's current age. Therefore, we can set up the equation:
\[ 36 - x = x \]

4. **Solve for \( x \)**:
- Rearranging the equation gives:
\[ 36 = x + x \]
\[ 36 = 2x \]
- Dividing both sides by 2:
\[ x = \frac{36}{2} = 18 \]

5. **Determine the son's current age**: The son is currently 18 years old.

6. **Calculate the son's age 5 years ago**:
- To find the son's age 5 years ago, subtract 5 from his current age:
\[ 18 - 5 = 13 \]

7. **Conclusion**: The son's age 5 years ago was 13 years.

### Summary of the Solution:
- The current age of the son is 18 years.
- The son's age 5 years ago was 13 years.