${B=}$ $\frac{36}{1.3.5}$ + $\frac{36}{3.5.7}$ + ..... + $\frac{36}{25.27.29}$
${=9.(}$ $\frac{4}{1.3.5}$ + $\frac{4}{3.5.7}$ + ...... + $\frac{4}{25.27.29}$${)}$
${=9.(}$ $\frac{1}{1.3}$ - $\frac{1}{3.5}$ + $\frac{1}{3.5}$ - $\frac{1}{5.7}$ + .... + $\frac{1}{25.27}$ - $\frac{1}{27.29}$ ${)}$
${=9.(}$ $\frac{1}{1.3}$ - $\frac{1}{27.29}$ ${)}$
${=9.(}$ $\frac{1}{3}$ - $\frac{1}{783}$ ${)}$
${=9.}$ $\frac{260}{783}$
${=}$ $\frac{260}{87}$