[eli5] Trying to teach to an autistic child why 4 – (-2) is 4 +2.

Question

Title. I know it goes like that, but as an non mathematician can’t explain it to him.

In: 0

Answer 1

The number line.
0 in the middle with minus numbers on the left and positive numbers on the right.

We always go from zero and to the right, addition, unless told otherwise.

a minus symbol means “move in the opposite direction” i.e. move left

when there is another minus symbol following that still means “move in the opposite direction” i.e. move to the right.

So you start at 4.
Then there is a minus sign saying “move in the opposite direction” I.e. to the left.

You then arrive at another minus sign which says “move in the opposite direction” i.e. to the right (you were moving left with the first minus)