Basically you solve this by elimination or substitution
So you first make an equation where
c represents numbers of children tickets and ‘a’ represents adult tickets
a+c= 160
2a+ 5c=476
Multiply first equation by -2 to cancel out the a after addition
-2a-2c =-320
When you add the above equation with 2a +5c=476 you get 3c=156 which means that c=52 so the number of children tickets sold = 52
Now you substitute this answer to any of the equations and work out the value of a
a+52=160
a= 108