No, 21- (5 plus 2) does NOT equal 23.
7 and 2/15 + 5 and 10/15 + 9 and 13/15 = 21 and 25/15 = 22 and 2/3
25
23
1 + 2 + 1000 + 300 + 23 + 12 = 1338
45 + 8 - 23 + 2 = 32
480
346
2x + 2 + 5x = 23 2x +5x = 23 -2 7x = 21 X = 3
As written, 215 5 + 2 x 10 = 25
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