[tex] \frac{1}{10}\ \textless \ \frac{10}{x}\ \textless \ \frac{1}{9} [/tex] daca rasturnam fractiile pozitive cea mica devine mai mare (exemplu [tex] \frac{1}{3}\ \textless \ \frac{4}{1}. rasturnate.\frac{3}{1}\ \textgreater \ \frac{1}{4} [/tex].
Deci rasturnate fratiile date ⇒ [tex] \frac{10}{1}\ \textgreater \ \frac{x}{10}\ \textgreater \ \frac{9}{1} [/tex], inmultind toti termeni cu acelas numar pozirtv sensul se pastreaza, deci inmultind cu 10 ⇒100>x>90 ⇒x∈{91;92;93; ... ;99}
