2016 AMC 12B Problem 1

With $a=\tfrac12,$ we have $a^{-1}=2.$ The numerator is $2\cdot2+\dfrac{2}{2}=4+1=5,$ and dividing by $a=\tfrac12$ gives $\dfrac{5}{\frac{1}{2}}=10.$ Thus, the correct answer is D.