Let x and y be the number of children and adults in the group, respectively. Therefore, the two equations are
[tex]\begin{gathered} x+y=56\to\text{ 56 tickets in total} \\ 3x+7y=284\to\text{ total cost of the tickets} \end{gathered}[/tex]Solve the system of equations as shown below
[tex]\begin{gathered} x=56-y \\ \Rightarrow3(56-y)+7y=284 \end{gathered}[/tex]Solving the former equation for y,
[tex]\begin{gathered} \Rightarrow168-3y+7y=284 \\ \Rightarrow4y=116 \\ \Rightarrow y=29 \end{gathered}[/tex]Finding x,
[tex]\begin{gathered} \Rightarrow x=56-29=27 \\ \Rightarrow x=27 \end{gathered}[/tex]The answer is 27 children and 29 adults in total.