1. The problem is to simplify the expression $\frac{a}{a}$. 2. The formula used here is the property of division where any non-zero number divided by itself equals 1, i.e., $\frac{x}{x} = 1$ for $x \neq 0$. 3. Since $a$ is in both numerator and denominator and assuming $a \neq 0$, we can simplify $\frac{a}{a} = 1$. 4. Therefore, the simplified form of $\frac{a}{a}$ is $1$.