I need a question to answer first.
8a+4s=840
a=s+30
8(s+30)+4s=840
12s+240=840
12s=600
s=50
A=s+30
a=50+30
a=80
The drama play sold 80 adult tickets
if you don't have a Unit Circle, this is a good time to get one, you'd need it, you can find many online.
Check the picture below.
Infinitely many, but they will all be proportional to each other