Đáp án:
$\dfrac{1}{2}$x +$\dfrac{3}{5}$(x-2)=3
<=> $\dfrac{1}{2}$x + $\dfrac{3}{5}$x -$\dfrac{6}{5}$ =3
<=> $\dfrac{1}{2}$x + $\dfrac{3}{5}$x = 3 + $\dfrac{6}{5}$
<=> $\dfrac{11}{10}$x = $\dfrac{21}{5}$
<=> x=$\dfrac{21}{5}$ : $\dfrac{11}{10}$
<=> x=$\dfrac{42}{11}$
Vậy x = $\dfrac{42}{11}$