Peter bought 24 tickets for 490. Adult tickets =25 and student tickets = 15. How many of each type did he buy?
a + s = 24 or s = 24-a
25a + 15s = 490
or
5a + 3s = 98 after dividing each term by 5
use substitution
5a + 3(24-a) = 98
solve for a, then you can find s