Thực hiện phep tính : 5/14 +1/6 : 7/9 ; -12/18 +15/45-8/16

$a,\dfrac{5}{14}+\dfrac{1}{6}:\dfrac{7}{9}$

$=\dfrac{5}{14}+\dfrac{1}{6}.\dfrac{9}{7}$

$=\dfrac{5}{14}+\dfrac{3}{14}$

$=\dfrac{8}{14}$

$=\dfrac{4}{7}$

$b,\dfrac{-12}{18}+\dfrac{15}{45}-\dfrac{8}{16}$

$=\dfrac{-2}{3}+\dfrac{1}{3}-\dfrac{1}{2}$

$=\dfrac{-4}{6}+\dfrac{2}{6}-\dfrac{3}{6}$

$=\dfrac{-4+2-3}{6}$

$=\dfrac{-5}{6}$