7/8 + ( 1/8 + 1/9 )
5/6 + ( 1/2 + 2/3 )
9/7 - ( 2/7 - 10/2 1 )
3/7 + 49/9 + 4/7
2\3+5\9-2\3+5\9
7/8 + ( 1/8 + 1/9 )
9/7 - ( 2/7 – 10/2 1 )
1/2+3/4-3/ 10= 19/20
2/9+5/6+ 1/3=25/ 18
Operation attribute
1, the properties of addition operation
From additive commutative law's associative law, it can be concluded that when several addends are added, the positions of addends can be exchanged at will; Or add a few addends first and then add them with other addends, and the sum remains the same. For example: 34+72+66+28 = (34+66)+(72+28) = 200.
2. The nature of subtraction operation
(1) A number minus the sum of two numbers is equal to subtracting each addend in the sum from this number in turn. For example:134-(34+63) =134-34-63 = 37.
(2) A number minus the difference between two numbers is equal to this number minus the minuend in the difference first and then minus the minuend. For example: 100-(32-15) =100-32+15 = 68+15 = 83.