1. **State the problem:** We need to express the number of circles as a fraction of the entire set of shapes. 2. **Identify total shapes and circles:** There are 21 shapes in total and 10 of them are circles. 3. **Write the fraction:** The fraction representing circles out of the total shapes is $$\frac{10}{21}$$. 4. **Simplify the fraction if possible:** 10 and 21 have no common factors other than 1, so the fraction is already in simplest form. 5. **Final answer:** The circles represent $$\frac{10}{21}$$ of the entire set.