Ta có \(\frac{11}{4}\)> \(\frac{x}{20}\)> \(\frac{5}{11}\)
=> \(\frac{605}{220}\)> \(\frac{11x}{220}\)> \(\frac{100}{220}\)
=> 605 > 11x > 100
=> 56 > x > 9
\(\frac{11}{4}>\frac{x}{20}>\frac{5}{11}\)
\(\Leftrightarrow\frac{605}{220}>\frac{11x}{220}>\frac{100}{220}\)
\(\Leftrightarrow\frac{55}{20}>\frac{x}{20}>\frac{9,\left(09\right)}{20}\)
\(\Rightarrow x\in\left\{11;22;33;44\right\}\)
Ta quy đồng mẫu số:
\(\frac{11}{4}\)>\(\frac{x}{20}\)>\(\frac{5}{11}\)
-> \(\frac{11.20.11}{4.20.11}\) > \(\frac{x.11.4}{4.20.11}\)> \(\frac{5.4.20}{4.20.11}\)
-> \(\frac{2420}{880}\)> \(\frac{44x}{880}\)> \(\frac{400}{880}\)
-> 2420 > 44x > 400
-> 44x thuộc {401;...;2419}
-> x thuộc {10;11;12;13;...;51;52;53;54}
