b) 5/4 . 12/7 - 3/2

* Hướng dẫn giải

b) $\frac{5}{4}.\frac{12}{7}-\frac{3}{2}$

$$\begin{gathered} =\frac{\mathrm{5.3.4}}{4.7}-\frac{3}{2} \\ =\frac{15}{7}-\frac{3}{2} \\ =\frac{15.2}{7.2}-\frac{3.7}{2.7} \\ =\frac{30}{14}-\frac{21}{14} \\ =\frac{9}{14} \end{gathered}$$