$\dfrac{5}{12}$ × $\dfrac{2}{3}$ + $\dfrac{2}{3}$ × $\dfrac{7}{12}$
= ( $\dfrac{5}{12}$ + $\dfrac{7}{12}$ ) × $\dfrac{2}{3}$
= $\dfrac{12}{12}$ × $\dfrac{2}{3}$
= $\dfrac{24}{36}$ = $\dfrac{2}{3}$
$\dfrac{13}{8}$ ÷ $\dfrac{3}{4}$ - $\dfrac{5}{8}$ ÷ $\dfrac{3}{4}$
= ( $\dfrac{13}{8}$ - $\dfrac{5}{8}$ ) ÷ $\dfrac{3}{4}$
= $\dfrac{8}{8}$ ÷ $\dfrac{3}{4}$
= $\dfrac{8}{8}$ × $\dfrac{4}{3}$
= $\dfrac{32}{24}$ = $\dfrac{4}{3}$
#nocopy
@bear