4-2 is 2 because if you start at 4 and move left 2 due to the subtraction of 2 then you land on 2 on the number line.
2-4 is -2 because if you start at 2 and move left 4 units due to subtraction of 4 then you have landed at -2 on the number line.
Also 2-4=-4+2=-(4-2). This means 2-4 and 4-2 will have opposite values. 2-4 is a negative number because you are taking a bigger positive number away from a smaller positive number. 4-2 is a positive value because you are taking a positive smaller value away from a bigger positive value. Any positive number are greater than any negative number.
