Odpowiedź:
U - cena biletu ulgowego
N - cena biletu normalnego
[tex]\left\{ \begin{array}{ll} U = N - 5 \\ 2N + 3U = 90 \end{array}[/tex]
2N + 3*(N - 5) = 90
2N + 3N - 15 = 90
5N = 105
N = 21
U = N - 5
U = 21 - 5
U = 16
[tex]\left\{ \begin{array}{ll} O = 16 \\ N = 21 \end{array}[/tex]