Răspuns :
[tex](2x+9x):11+2x\ \textless \ 60 \\ \\ 11x:11+2x\ \textless \ 60 \\ \\ x+2x\ \textless \ 60 \\ \\ 3x\ \textless \ 60 \\ \\ x\ \textless \ 20 \Rightarrow \boxed{x \in \{0,1,2,3,...,19\}}[/tex]
Pai dupa ce calculezi x-ul, care e usor de calculat, afli ca numerele sunt 0, 1, 2, 3, ...19.