a) ( x- $\frac{1}{2}$ ) : $\frac{1}{3}$ + $\frac{5}{7}$ =$\frac{68}{7}$
=> x - $\frac{1}{2}$ = ($\frac{68}{7}$ -$\frac{5}{7}$). $\frac{1}{3}$
=> x - $\frac{1}{2}$ = 3
=> x = 3 +$\frac{1}{2}$
=> x = $\frac{7}{2}$
Vậy x = $\frac{7}{2}$
b) 70 : $\frac{4x+120}{x}$ = $\frac{1}{2}$
=> $\frac{4x+120}{x}$ = 70 :$\frac{1}{2}$
=> $\frac{4x+120}{x}$ = 140
=> 4x+ 720 = 140x
=> 140x - 4x = 720
=> 136x = 720
=> x= $\frac{720}{136}$ = $\frac{90}{17}$
