\(\frac{2}{5}< \frac{x}{8}< \frac{3}{5}\)
\(\Rightarrow\frac{16}{40}< \frac{5x}{40}< \frac{24}{40}\)
\(\Rightarrow5x\in\left\{17;18;19;20;21;22;23\right\}\)
\(\Rightarrow x\in\left\{\frac{17}{5};\frac{18}{5};\frac{19}{5};4;\frac{21}{5};\frac{22}{5};\frac{23}{5}\right\}\)
chúc bạn học tốt
=> 16/40<5x/40<24/40
=> 16<5x<24
=> x= 4
nếu x thuộc Z