This is because the first point in the parenthesis is x and the second is y. If we know this, we can substitute -5 in for x and -6 in for y to get that -15 - (-12) > -4. When you subtract by a negative number, it is the same as adding by that number, so -15 - (-12) = -15 + 12, so we get that -3 > -4. This is true because when you have negative numbers, the lesser negative number is the greater one (Ex. -5 > -6).
