'Able' in the Bible

Now therefore, come make a bargain with my master the king of Assyria, and I will give you two thousand horses, if you are able on your part to set riders on them.

Thus says the king, ‘Do not let Hezekiah deceive you, for he will not be able to deliver you;

“Stand fast now in your spellsAnd in your many sorceriesWith which you have labored from your youth;Perhaps you will be able to profit,Perhaps you may cause trembling.