[tex]\dfrac{a}{b} = \dfrac{\dfrac{1}{22}-\dfrac{1}{33}+\dfrac{1}{44}-\dfrac{1}{55}}{\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{4}-\dfrac{1}{5}} =\dfrac{\dfrac{1}{11}\cdot \Big(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{4}-\dfrac{1}{5}\Big)}{\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{4}-\dfrac{1}{5}} = \dfrac{1}{11}[/tex]