2011 AMC 12B Problem 1

The sums are $2+4+6=12$ and $1+3+5=9,$ so the expression equals $\dfrac{12}{9}-\dfrac{9}{12}=\dfrac{4}{3}-\dfrac{3}{4}.$ Over a common denominator this is $$\dfrac{16}{12}-\dfrac{9}{12}=\dfrac{7}{12}.$$ Thus, the correct answer is C.