1.60%X+15=40

速度问题.不打解了.
1.60%X+15=40
60%x=40-15
x=25/60%
x=125/3
2.5/10+(7/10-1/4)除1/2
=1/2+9/20/1/2
=1/2+9/10
=7/5
3.(1/2+1/3+1/4)x12
=6+4+3
=13
4.7/20x99+7/20
=7/20x(99+1)
=35
5.20/3x1/2-1/34
=10/3-1/34
=337/1.2
6.15-4.25-5.75
=15-(4.25+5.75)
=15-10
=5
7.25分米:0.25厘米
=250厘米:0.25厘米
=25000厘米:25厘米
=1000:1