${A=}$ $\frac{1}{8.11}$ ${+}$ $\frac{1}{11.14}$ ${+....+}$ $\frac{1}{155.158}$
${=}$ $\frac{1}{8}$ ${-}$ $\frac{1}{14}$ ${+}$ $\frac{1}{11}$ ${-}$ $\frac{1}{14}$ ${+....+}$ $\frac{1}{155}$ ${-}$ $\frac{1}{158}$
${=}$ $\frac{1}{8}$ ${-}$ $\frac{1}{155}$
${=}$ $\frac{147}{1240}$.