Chapter 5 - Relationships Within Triangles - 5-5 Indirect Proof - Practice and Problem-Solving Exercises - Page 321: 18

If a number ends in $5$, then it is divisible by $2$.

For the first step in an indirect proof, we have to negate the "then" part of the statement. So we can write that if a number ends in $5$, then it is divisible by $2$.