Đáp án:
x=14,y=40,z=64
Giải thích các bước giải:
\(\left\{ \begin{array}{l}
\frac{x}{y} = \frac{7}{{20}}\\
\frac{y}{z} = \frac{5}{8}\\
2x{\rm{ }} + {\rm{ }}5y{\rm{ }} - {\rm{ }}2z{\rm{ }} = 100
\end{array} \right. \leftrightarrow \left\{ \begin{array}{l}
x = \frac{{7y}}{{20}}\\
z = \frac{{8y}}{5}\\
2x{\rm{ }} + {\rm{ }}5y{\rm{ }} - {\rm{ }}2z{\rm{ }} = 100
\end{array} \right. \leftrightarrow \left\{ \begin{array}{l}
x = \frac{{7y}}{{20}}\\
z = \frac{{8y}}{5}\\
2.\frac{{7y}}{{20}}{\rm{ }} + {\rm{ }}5y{\rm{ }} - {\rm{ }}2.\frac{{8y}}{5}{\rm{ }} = 100
\end{array} \right. \leftrightarrow \left\{ \begin{array}{l}
x = \frac{{7y}}{{20}}\\
z = \frac{{8y}}{5}\\
\frac{{5y}}{2}{\rm{ }} = 100
\end{array} \right. \leftrightarrow \left\{ \begin{array}{l}
y = 40\\
x = \frac{7}{{20}}.40 = 14\\
z = \frac{8}{5}.40 = 64
\end{array} \right.\)
