Question 145195
Okay, let "x"= adult's ticket, and "y"= child's ticket
since 80 tickets  were sold, "x+y = 80" right? ---------- eqn 1
We know the cost for each adult's ticket and also for the child that totals $1040. Putting that into equation,
$18(x) + $10(y) = $1040  --------------- eqn 2
In eqn 1 we get, "y=80-x", and substitute this in eqn 2:
18(x)+ 10(80-x) = 1040
18x+800-10x=1040
8x=1040-800
x=30 ---------------- This the number of adult's ticket sold
For  y, go back eqn 1,
30+y=80
y=80-30=50 ---------------- This the number of child's ticket sold
In doubt? Go back eqn 2,
18(30)+10(50) = 1040
540+500=1040
$1040=$1040
Thank you,
Jojo