The group that went to the movies was 1 adult and x children.
Each adult ticket costs $15 and each child ticket costs $10
The total cost of the tickets can be representd as C
C=15y+10x
Where y is the number of adults tickets brought.
So for C=$55 and y=1 the total cost can be calculated as:
[tex]55=15+10x[/tex]From this expression you can calculate the number of children tickets bought
[tex]\begin{gathered} 55-15=10x \\ 40=10x \\ \frac{40}{10}=\frac{10x}{10} \\ 4=x \end{gathered}[/tex]4 children went to the movies.
