$\text {$\frac{1}{2}$×x+ x×$\frac{7}{2}$+x×$\frac{3}{2}$ =100 }$
$\text {⇔x×($\frac{1}{2}$+ $\frac{7}{2}$+ $\frac{3}{2}$) =100}$
$\text {⇔x×$\frac{11}{2}$ =100 }$
$\text {⇒x= $\frac{200}{11}$ }$
$\text {Vậy x=$\frac{200}{11}$ }$
$\text {Chúc bạn học tốt~}$
$\text {@lamtung2}$