A theater has a seating capacity of 900 and charges 4$ for children, 6$ for students, and 8$ for adults. At a certain screening with full attendance, there were half as many adults as children and students combined. The receipts totaled 5600$. How many people from each group attended the show ?

Answer 1

so, what do you know?
c+s+a = 900
a = (c+s)/2
4c+6s+8a = 5600

3 equations in 3 unknowns. Just solve them for c,s,a