Given data:
The total numbers of tickets purchased is a+b=20.
The total cost of the tickets is 15a+10b=225.
The first equation can be written as,
[tex]a=20-b[/tex]Substitute the above expression in the second equation.
[tex]\begin{gathered} 15(20-b)+10b=225 \\ 300-15b+10b=225 \\ -5b=-75 \\ b=15 \end{gathered}[/tex]The value of a is,
[tex]\begin{gathered} a=20-15 \\ =5 \end{gathered}[/tex]Thus, the numbers of tickes purchased by children are 15, and the numbers of tickets purchased by adults are 5.
