Rút gọn biểu thức

$$\begin{gathered} a)\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{100.103} \\ b)\frac{3}{1.4}+\frac{6}{4.10}+\frac{9}{10.19}+\frac{12}{19.31}+\frac{15}{31.46}+\frac{18}{46.64} \end{gathered}$$