0.75+(-2又5/7)-(-0.125)+(-12又5/7)-4又1/8

0.75+(-2又5/7)-(-0.125)+(-12又5/7)-4又1/8


∵原式=0.75-19/7+0.125-89/7-33/8=0.75+0.125-19/7-89/7-33/8=0.875-108/7-33/8
=-18.68
∴0.75+(-2又5/7)-(-0.125)+(-12又5/7)-4又1/8=18.68



解比例x:7.5=2.1:1.8 6.5x:3=10:9


x:7.5=2.1:1.8
1.8x=7.5*2.1
x=7.5*2.1/1.8
x=8.75
6.5x:3=10:9
9*6.5x=10*3
x=30/(9*6.5)
x=20/39



0.2(5x-1)+5(x-1)=0.8解比例:6(x-1)=7(x-3)
我十分急,


解方程:0.2(5x-1)+5(x-1)=0.8
x-0.2+5x-5=0.8
6x=5.2+0.8
x=1
解比例:6(x-1)=7(x-3)
6x-6=7x-21
7x-6x=21-6
x=15