The operation $\star$ is defined as $a \star b = a + \frac{a}{b}$. What is the value of $12 \star 3$?
To find $12 \star 3$, I need to plug in $a = 12$ and $b = 3$ into the definition of $\star$. That gives me $12 \star 3 = 12 + \frac{12}{3}$. I can simplify this expression by performing the arithmetic operations. I get $12 \star 3 = 12 + 4 = 16$. 