Question 862103
This is a cost revenue type problem and an application of a simple linear system.  Here is restating and refining your analysis:


child ticket price, 3 dollars per ticket
adult ticket price, 5 dollars per ticket
x = count of child tickets
y = count of adult tickets


ACCOUNT FOR AMOUNT OF TICKETS:  {{{highlight(x+y=145)}}}
ACCOUNT FOR TICKET SALES:  {{{highlight(3x+5y=663)}}}


Work at understanding that.  Once you understand that process and those resulting equations, you should find that solving for x and y is an easy task.