If the first quadrant, you start at (6, 5) and move 3 units left

Left means that you are moving along the x axis. The coordinates are 6 (x), and 5 (y). You don't need to do anything to the y coordinates, because you are moving along the x axis. So all you have to do is imagine a number line. You are at 6, and you have to move 3 to the left, or the negative direction. You will be at 3,5.

Answer: 3,5