#### Answer

$t = 25 - n$

#### Work Step by Step

The first figure has 24 tiles. The second has 23. The third has 22, and so on. It is clear each figure has one tile less than the previous figure.
Therefore, as n (the input) gets bigger by 1, the number of tiles (the output) gets smaller by 1. 24 is 1 less than 25. 23 is 2 less than 25, etc. So, 25 minus n (the input) gives you the number of tiles (the output).
The process column shows this for each input and output.