you don't want to exceed 525, so you set the inequality to be
[tex]525\geq 175+85x[/tex]
we can think of the max as just
[tex]525=175+85x[/tex]
solve for x
[tex]85x=350[/tex]
[tex]x=4ish[/tex]
(note: always round down so that you don't exceed the max. ex. you could round to 4.11 instead of 4.12. x=4.12 would give you a value greater than 525)
