No, 21- (5 plus 2) does NOT equal 23.
23
1 + 2 + 1000 + 300 + 23 + 12 = 1338
45 + 8 - 23 + 2 = 32
346
2x + 2 + 5x = 23 2x +5x = 23 -2 7x = 21 X = 3
33
23
Well, 8+23+2 is addition, but I assume you mean what is the propery that makes 8+23+2, 2+23+8, and 23+8+2, etc., all equal the same thing, and that would be the associative property
45
- 23
45