Stem + にくい + です = hard/difficult to […]
たべにくいです = hard to eat
Stem + やすい + です = easy to […]
よみやすいです = easy to read
These are now い-Adjectives! Mostly conjugated to past tense, although the other forms do exist too.
かきにくかった です = was hard to write
ならいやすかった です = was easy to learn