765
87+42+78 = 207
187 of course !
19 + (44 + 23) = (19 + 44) + 23
738
Assuming that there is a "plus" after the second 58, the answer is - the associative property of addition.
348
9 plus 87 equals 96.
87 + 15 + 48 = 150
765
23 - 110 = -87
87+42+78 = 207
1 + 55 + 345 + 87 + 98 = 586
87 + 19 = 106
99 + 87 = 186
87+7= 94
34 + 98 + 98 + 87 + 32 = 349