@SANGOFFICIAL
a, $\frac{7}{4}$ - $\frac{2}{3}$ ÷ $\frac{5}{3}$
= $\frac{7}{4}$ - $\frac{2}{3}$ × $\frac{3}{5}$
= $\frac{7}{4}$ - $\frac{2}{5}$
= $\frac{35}{20}$ - $\frac{8}{20}$
= $\frac{27}{20}$
b, $\frac{24}{42}$ ÷ 4 × $\frac{7}{4}$
= $\frac{24}{42}$ × $\frac{1}{4}$ × $\frac{7}{4}$
= $\frac{1}{4}$