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求未知数x的值:x+ 1 2 x= 4 5 ...

①12x+34x=1 54x=1 54x×45=1×45 x=45②x:25=1.2:75 75x=25×1.2 75x=3075x÷75=30÷75 x=0.4

解:根据比例的基本性质: 4/5:×=2:0.75 2x=4/5*0.75 2x=3/5 x=3/5÷2 x=3/10

根据题意可得:(1) 2 3 x+ 1 3 = 4 5 , 2 3 x+ 1 3 - 1 3 = 4 5 - 1 3 , 2 3 x= 7 15 , 2 3 x÷ 2 3 = 7 15 ÷ 2 3 ,x= 7 10 ;(2)18:x= 3 10 : 3 5 , 3 10 x=18× 3 5 , 3 10 x= 54 5 , 3 10 x÷ 3 10 = 54 5 ÷ 3 10 , x=36.

(1)2x+3.8x=40.6, 5.8x=40.6, 5.8x÷5.8=40.6÷5.8, x=7;(2) 2 5 x- 3 4 = 1 4 , 2 5 x- 3 4 + 3 4 = 1 4 + 3 4 , 2 5 x=1, 2 5 x× 5 2 =1× 5 2 , x= 5 2 ;(3) 5 8 = x-2 10 , 8×(x-2)=50,8×(x-2)÷8=50÷8, x-2=6.25, x-2+...

(1)8:x=3:2.4, 3x=2.4×8, 3x÷3=19.2÷3, x=6.4;(2)2x+25x=18, (2+25)x=18, 125x=18, 125x×512=18×512, x=152.

(1)x+40%x=28 1.4x=28 1.4x÷1.4=28÷1.4 x=20;(2)15x÷12=3 15x÷12×12=3×12 15x=32 15x×5=32×5 x=152;(3)x-15x=310 45x=310 45x×54=310×54 x=38;(4)56x-14=0.75 56x-14+14=0.75+14 56x=1 56x×

x@(4@2)=x@〔(4+2)/2〕=x@3=(x+3)/3=1.2 解得x=0.6

(1)6(x-0.5)=30, 6(x-0.5)÷6=30÷6, x-0.5=5, x-0.5+0.5=5+0.5, x=5.5;检验:把x=5.5代入原方程,左边=6×(5.5-0.5)=30,右边=30,左边=右边,所以,x=5.5是原方程的解;(2) 1.2 7.5 = 0.4 x , 1.2x=0.4×7.5, 1.2x=3,1.2x÷1.2=...

①1-34x=0.6 1+34x-34x=0.6+34x 1=0.6+34x0.6-0.6+34x=1-0.6 34x=25 34x×43=25×43 x=815②23x+0.5x=42 46x+36x=42 76x=42 76x×67=42×67 x=36③8.6:7=x:1.4 7x=8.6×1.4 7x÷7=8.6×1.4÷7 x=1.72

(1) 1.2 7.5 = 0.4 x , 1.2x=7.5×0.4, 1.2x=3, 1.2x÷1.2=3÷1.2, x=2.5;(2)1+ 2 5 X=63× 1 9 , 1+ 2 5 X=7, 1+ 2 5 X-1=7-1, 2 5 X=6, 2 5 X÷ 2 5 =6÷ 2 5 , X=15;(3)10X-9×1.8=1.8, 10X-16.2=1.8, 10X-16.2+16.2=1.8+16.2,...

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