Given:
total of 224 visitors
older than 18 paid $12
18 and below paid $8
total collection 2,520
Let l be visitors older than 18 and m be visitors 18 and below.
l + m = 224
12l + 8m = 2,520
l = 224 - m
12(224 - m) + 8m = 2520
2688 - 12m + 8m = 2520
-4m = 2520 - 2688
-4m = -168
m = -168/-4
m = 42 number of visitors 18 and below.
l = 224 - m
l = 224 - 42
l = 182 number of visitors older than 18.
12(182) + 8(42) = 2520
2184 + 336 = 2520
2520 = 2520