a, A= 1-$\frac{3}{4.7}$-$\frac{3}{7.10}$-...-$\frac{3}{91.94}$
= 1-$\frac{1}{4}$+$\frac{1}{7}$-$\frac{1}{7}$+$\frac{1}{7}$-...-$\frac{1}{91}$+$\frac{1}{94}$
= 1-$\frac{1}{4}$+$\frac{1}{94}$
= $\frac{143}{188}$
b, B= 2-$\frac{2}{3.5}$-....-$\frac{2}{63.65}$
= 2-$\frac{1}{3}$+$\frac{1}{5}$-...-$\frac{1}{63}$+$\frac{1}{65}$
= 2-$\frac{1}{3}$+$\frac{1}{65}$
= $\frac{328}{195}$