3a + a - 15 = 225 . your substituting b(a-15) into the first equation. <span />
If you are talking about a graph:
The input would be the number of adult tickets.
The output would be the amount of money.
If you talking about it normally:
The input would be the amount of money.
The output would be the number of adult tickets.
25-4x=16-4x
25-4x+4x=16-4x+4x
25=16
No solution
Contradiction