$30×(\dfrac{1}{5}+\dfrac{1}{3})$
$=30×\dfrac{1}{5}+30×\dfrac{1}{3}$
$=6+10$
$=16$
$\dfrac{3}{4}×\dfrac{1}{9}+\dfrac{1}{4}÷9$
$=\dfrac{3}{4}×\dfrac{1}{9}+\dfrac{1}{4}×\dfrac{1}{9}$
$=(\dfrac{3}{4}+\dfrac{1}{4})×\dfrac{1}{9}$
$=1×\dfrac{1}{9}=\dfrac{1}{9}$
$7.24×0.6-0.24×0.6$
$=(7.24-0.24)×0.6$
$=7×0.6$
$=4.2$