a) $4\dfrac{1}{3}:\dfrac{x}{4}=6:0,3$
$\dfrac{13}{3}.\dfrac{4}{x}=6.\dfrac{10}{3}$
$\dfrac{13}{3}.\dfrac{4}{x}=20$
$\dfrac{4}{x}=20.\dfrac{3}{13}=\dfrac{60}{13}$
$60x=4.13=52$
⇒ $x=\dfrac{52}{60}$
b) $\dfrac{x}{10}=\dfrac{y}{5}$ ⇒ $\dfrac{x}{20}=\dfrac{y}{10}$
$\dfrac{y}{2}=\dfrac{z}{5}$ ⇒ $\dfrac{y}{10}=\dfrac{z}{25}$
⇒ $\dfrac{x}{20}=\dfrac{y}{10}=\dfrac{z}{25}$
⇒ $\dfrac{2x}{40}=\dfrac{3y}{30}=\dfrac{4z}{100}$
mà $2x-3y+4z=330$
Áp dụng dãy tỉ số bằng nhau:
⇒ $\dfrac{2x}{40}=\dfrac{3y}{30}=\dfrac{4z}{100}=\dfrac{2x-3y+4z}{40-30+100}=\dfrac{330}{110}=3$
⇒ $\dfrac{x}{20}=3⇒x=3.20=60$
$\dfrac{y}{10}=3⇒y=3.10=30$
$\dfrac{z}{25}=3⇒z=25.3=75$
Vậy $(x,y,z)=(60,30,75)$
