let x be senior tickets and y child tickets
[tex]\begin{gathered} \begin{cases}8x+10y=156 \\ 12x+y=150\end{cases}\rightarrow\begin{cases}8x+10y=156 \\ -120x-10y=-1500\end{cases}\rightarrow \\ -112x=-1344\rightarrow x=\frac{1344}{112}=12 \end{gathered}[/tex]so the senior ticket cost $12 and the child ticket cost $6
[tex]12\cdot12+y=150\rightarrow y=150-144=6[/tex]