1. The problem is to convert the fraction $\frac{12}{15}$ into a mixed number in the form $a \frac{b}{c}$. 2. First, simplify the fraction $\frac{12}{15}$ by finding the greatest common divisor (GCD) of 12 and 15, which is 3. 3. Divide numerator and denominator by 3: $$\frac{\cancel{12}^4}{\cancel{15}^5} = \frac{4}{5}$$ 4. Since $\frac{4}{5}$ is less than 1, the mixed number form is $0 \frac{4}{5}$. 5. Therefore, $\frac{12}{15}$ as a mixed number is $0 \frac{4}{5}$, or simply $\frac{4}{5}$ since the whole number part is zero.