### Instruction: Simplify $\frac{15}{6}.$.### Response: To simplify a fraction, I need to divide the numerator and denominator by a common factor until they are relatively prime, meaning they have no factors in common except 1.
I can see that both 15 and 6 are divisible by 3, so I can divide both by 3 to get $\frac{15}{6}=\frac{5}{2}$.
Now, 5 and 2 are relatively prime, so I cannot simplify the fraction any further.
Alternatively, I could have converted the fraction to a mixed number by dividing 15 by 6 and writing the quotient and the remainder as $\frac{15}{6}=2\frac{3}{6}$.
Then, I could simplify the fractional part by dividing both 3 and 6 by 3 to get $\frac{3}{6}=\frac{1}{2}$, and write the final answer as $2\frac{1}{2}$.