I have searched and read articles and questions available regarding いけない and i do understand that it means that something cannot be done (you mustn't...).
But i'm a bit unsure about it's meaning in this sentence :
Roughly i translate it as
since that hotel is far, it seems that 20minutes walking there is not enough time.
I'm confused about what 歩いて20ぷん means : v-て + noun?
And いけない is must not do, if we use that literal meaning, it becomes we must not walk 20 minutes... So what is the meaning of いけない in here?