Oh, well, it doesn’t have to be spatial concepts. Anything with a notion of direction will do. We could do it temporally, for example.
That having been said, if you really just need to see it demonstrated, then you can illustrate the spatial example for yourself on a piece of paper. Draw an arrow, any arrow you want. Call that arrow A.
Now, anywhere you like, draw another arrow twice as long as A, but pointing in the opposite direction from A. Call that arrow B. By definition, B = -2 * A, since -2 * A just means any arrow twice as long as A but pointing in the opposite direction from A.
Now draw an arrow three times as long as B, but pointing in the opposite direction from B. Call that arrow C. By definition, C = -3 * B = -3 * -2 * A.
Finally, draw an arrow 6 times as long as the original A, pointing in the same direction as A. Call that arrow D. By definition, D = 6 * A.
Do C and D have the same length and point in the same direction? If so, then C = D, and you’ve shown that -3 * -2 * A = 6 * A.
If not, then something very interesting has happened.
I’ve illustrated with -2 and -3 but we can make it much much simpler, trivially so:
Draw an arrow. Call that arrow X.
Draw another arrow, just as long as X, but facing the opposite direction from X. Call this Y = -1 * X.
Draw another arrow, just as long as Y, but facing the opposite direction from Y. Call this Z = -1 * Y.
Finally, draw an arrow 1 times as long as X, facing in the same direction as X. Call this arrow Q = 1 * X.
Do Z and Q have the same length and direction? Then you’ve shown that -1 * -1 * X = 1 * X.