How many men did David kill?

700 men in chariots and 40,000 horsemen

And David slew the men of seven hundred chariots of the Syrians, and forty thousand horsemen. 2 Samuel 10:18

7000 men in chariots and 40,000 footmen

David slew of the Syrians seven thousand men which fought in chariots, and forty thousand footmen. 1 Chronicles 19:18