b) (x-$\dfrac{1}{2}$) :$\dfrac{1}{3}$ +$\dfrac{5}{7}$ =9$\dfrac{5}{7}$
=> (x-$\dfrac{1}{2}$) : $\dfrac{1}{3}$ + $\dfrac{5}{7}$ = 9 + $\dfrac{5}{7}$
=>(x-$\dfrac{1}{2}$) : $\dfrac{1}{3}$ = 9
=> (x-$\dfrac{1}{2}$) . 3 = 9
=>x - $\dfrac{1}{2}$ = 9 : 3
=> x -$\dfrac{1}{2}$ = 3
=> x = 3 + $\dfrac{1}{2}$
=> x = $\dfrac{6}{2}$ + $\dfrac{1}{2}$ = $\dfrac{7}{2}$
Vậy x = $\dfrac{7}{2}$
e)$\dfrac{x+3}{-15}$ = $\dfrac{1}{3}$
=>$\dfrac{x+3}{-15}$ = $\dfrac{-1}{-3}$
=>$\dfrac{x+3}{-15}$ = $\dfrac{-5}{-15}$
=> x+3 = -5
=> x =-5 - 3
=> x = -8
Vậy x =-8
