Strength checks?

Hi again.

I'm using Harlowe. I used this code in order to allow characters to set their attack:

Attack: [$Attack]<Attack| (link-repeat: "+")[(if: $points > 0)[(set: $points -= 1)(set: $Attack += 1)(replace: ?Attack)[$Attack](replace: ?points)[$points]]] / (link-repeat: "-")[(if: $Attack > 0)[(set: $Attack -= 1)(set: $points += 1)(replace: ?Attack)[$Attack](replace: ?points)[$points]]]

How do I code it so that their attack has an effect? You're meant to pass a strength check to open a chest, and I've got:

(if: $Attack is >5)[text here [[Open chest.]]]

But obviously, that's not working, and I'm not sure how to edit it.

Sorry for being such a novice!