[tex]\it n:24=c\ rest\ r \Rightarrow \begin{cases} \it n=24c+r\\ \\ \it r<24\end{cases} \\ \\ \\ Dar,\ din\ enun\c{\it t},\ se\ \c{s}tie\ c\breve a\ r>21,\ deci\ \ r\in\{22, \ \ 23\} \Rightarrow \\ \\ \\ \Rightarrow n\in\{24c+22,\ \ 24c+23\}[/tex]
Deoarece, n are două cifre, vom obține:
[tex]\it n\in\{0+22,\ \ 24+22,\ \ 48+22,\ \ 72+22,\ \ 0+23,\ \ 24+23,\ \ 48+23,\ \ 72+23\}\\[/tex]
Suma acestor numere este: S = 4 · 22 + 4 · 23 +2 ·24 +2 · 48 + 2 · 72
