ANSWER
[tex]\$12[/tex]EXPLANATION
Let the price of one senior ticket be s.
Let the price of one child ticket be c.
Three senior tickets and one child ticket sold for $40. This implies that:
[tex]3s+c=40[/tex]Three senior tickets and two child tickets sold for $52. This implies that:
[tex]3s+2c=52[/tex]From the first equation, make 3s the subject of the formula:
[tex]3s=40-c[/tex]Substitute this into the second equation:
[tex]40-c+2c=52[/tex]Solve the equation for c by collecting like terms:
[tex]\begin{gathered} 2c-c=52-40 \\ \Rightarrow c=\$12 \end{gathered}[/tex]Therefore, a child ticket goes for $12.