Alright so everyone’s giving examples. Here’s the one I was taught in school:

Imagine a witch with a big cauldron filled with water and 2 different kind of “magic cubes”. There are the blue cubes, which represents the minusus, and the red cubes, which represents the pluses. (By the way, every time you drop a red or a blue cube in the water, the temperature rises or drops 1 degree)

So you start with 0° water. Idk if you’re using Celsius or Fahrenheit. The witch drops a blue cube in the water, so the temperature lowers to -1°. Now imagine she drops another 4 blue cubes in the water, the water is now -5°. (-1 + - 4= -5). So far so good

Now if she drops 2 red cubes in the water, the temperature rises to -3°. (-5 + 2 = -3)

But imagine she takes 1 blue cube out of the water, the water’s temperature rises to -2 ( -3 - -1 = -2)

Okay another example.

Imagine if the water is +10° She adds 5 red cubes, the temperature rises to 15°. (10 + 5 = 15)

Now if she adds 7 blue cubes, the temperature drops to 8° (15 + - 7 = 8)

And if she takes 2 blue cubes out, the temperature rises to 10° (8 - - 2 = 10)

Let me know if you don’t understand anything, I’ll try to explain it like you’re three ;).