'Able' in the Bible

Now therefore give pledges, I pray thee, to my master the king of Assyria, and I will give thee two thousand horses, if thou be able on thy part to set riders upon them.

Thus saith the king, Let not Hezekiah deceive you: for he shall not be able to deliver you.

Therefore shall evil come upon thee; thou shalt not know from whence it riseth: and mischief shall fall upon thee; thou shalt not be able to put it off: and desolation shall come upon thee suddenly, which thou shalt not know.

Stand now with thine enchantments, and with the multitude of thy sorceries, wherein thou hast laboured from thy youth; if so be thou shalt be able to profit, if so be thou mayest prevail.