'Able' in the Bible

Now therefore, I pray thee, give pledges 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 will not be able to deliver you:

Therefore shall evil come upon thee; thou shalt not know the dawning thereof: and mischief shall fall upon thee; thou shalt not be able to put it away: and desolation shall come upon thee suddenly, which thou knowest not.

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