Find the radius of a circle whose circumference is equal to the sum of the circumference of two circles of radii `15` `cm` and `18` `cm` .

Explanation

To find the radius of a circle whose circumference is equal to the sum of the circumferences of two circles with radii 15 cm and 18 cm, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Circumference Formula**:
The circumference \( C \) of a circle is given by the formula:
\[
C = 2\pi r
...