Um... e daí?
Achar means, "to think" as in to have an opinion, for example, I find that leagues are detrimental to studying a language.
So, backed up by the Portuguese Course Contributor here (DanMoller) as linked in my previous comment that you replied to here, "I find that..." should also be accepted as correct for this exercise. Or, it should be changed to "pensar em" instead.
Just a few quick examples pulled off a google search:
- I find the whole Direct Vs Indirect object thing quite troubling
- I find this especially useful
- I find it difficult to believe that there is an argument
- So I find it so important to focus on grammar rules especially for non-native speakers
- I should say that I find myself disagreeing with you here
- I find my grammar book acts as a map to know where my problems are
- I find the chair comfortable