1、7/25×4/9+7/25×5/9
=7/25×(4/9+5/9)
=7/25×1
=7/25
2、60×(1/12+1/15+1/4)
=60×1/12+60×1/15+60×1/4
=5+4+15
=24
3、(5/12-3/8)×72
=5/12×72-3/8×72
=30-27
=3
4、6/7-5/24÷7/12
=6/7-5/24×12/7
=12/14-5/14
=7/14
=1/2
5、[3/4×(7/16-1/4)]÷9/13
=3/4×（7/16-4/16）×13/9
=1/4×3/16×13/3
=13/64
6、2/3-7/8+1/3
=(2/3+1/3)-7/8
=1-7/8
=1/8
7、5/6-(3/7-1/6)
=(5/6+1/6)-3/7
=1-3/7
=4/7
8、1-1/3-2/3
=1-(1/3+2/3)
=1-1
=0
9、1+3/5-1/10
=1+6/10-1/10
=1+1/2
=1又1/2
10、3/8-12/13+5/8
=3/8+5/8-12/13
=1-12/13
=1/13
11、1-(1/2-3/4)
=1+3/4-2/4
=1+1/4
=5/4
12、1-1/2-1/4
=1/2-1/4
=2/4-1/4
=1/4
13、2/7-8/9+5/7
=(2/7+5/7)-8/9
=1-8/9
=1/9
14、2-1/4-3/4
=2-(1/4+3/4)
=2-1
=1
15、1/2-(3/8-1/2)
=1/2+1/2-3/4
=1-3/8
=5/8
16、2.64×1.7-2.64×0.7
=2.64×(1.7-0.7)
=2.64×1
=2.64
17、31.5×1.07-3.15×0.7
=3.15×10.7-3.15×0.7
=3.15×(10.7-0.7)
=3.15×10
=31.5
18、2.7×5.7-2.7+5.3×2.7
=2.7×(5.7-1+5.3)
=2.7×10
=27
19、0.625÷0.125×0.8
=(0.625×0.8)×8÷(0.125×8)
=0.5×8÷1
=4
20、18.6×6.1+3.9×18.6
=18.6×(6.1+3.9)
=18.6×10
=186
