
Anonymous A. answered 06/06/19
Astrophysics at Caltech/NASA Jet Propulson Laboratory
You have three variables: Let `C` be the number of children, `T` the number of teenagers, and `A` the number of adults. You're told that 1200 people go to the zoo every day. In math terms, that `C + T + A = 1200`.
You're also told that total revenue was $5300. The total revenue from children is `$4 * C`, from teenagers is `$5 * T`, and from adults is `$6 * A`. All together, you have `4C + 5T + 6A = 5300`.
Finally, you're told that for every three teenagers (T/3), there are eight children (C/8). That is `T/3 = C/8`.
So we have three unknowns, C, T, A. And we have three equations
C + T + A = 1200
4C + 5T + 6A = 5300
8T = 3C