When you subtract a number, you get the same result as when you add the opposite of that number. Why?

Step-by-step explanation:

Well, the opposite of a number is the same number with the opposite sign. For example, the opposite of -1 is 1.

So, say we have an equation where we're subtracting a number, for example, 2-1, which obviously equals 1. Now, if we add the opposite of 1 to 2, we get the equation 2+(-1) which still equals 1.

I hope this helps!

the first one, all those points on the line just make a strait line.