you can think of the -axis as number line add another number line going up and down for the -axis if you put these two number lines togetheryou have cartesian coordinate system like in figure - adding positive number (or subtracting negative numberwould move the knight up the number lineand subtracting positive number (or adding negative numberwould move the knight down the coordinate is called the origin math tricks subtracting and adding negative numbers is easy when you have number line in front of you it can also be easy without number line too here are three tricks to help you add and subtract negative numbers by yourself trick " minus eats the plus sign on its leftwhen you see minus sign with plus sign on the leftyou can replace the plus sign with minus sign imagine the minus sign "eatingthe plus sign to its left the answer is still the samebecause adding negative value is the same as subtracting positive value - and both evaluate to figure - trick adding positive and negative number trick "two minuses combine into pluswhen you see the two minus signs next to each other without number between themthey can combine into plus sign the answer is still the samebecause subtracting negative value is the same as adding positive value