6x+450-450=3200-440

6x=2760

6x÷6=2760÷6

X=460

（5）X-0.8X=6

0.2x=6

0.2x÷0.2=6÷0.2

X=30

(6)12x-8x=4.8

4x=4.8

4x÷4=4.8÷4

X=1.2

(7)7.5+2X=15

2x+7.5-7.5=15-7.5

2x=7.5

2x÷2=7.5÷2

X=3.75

(8)1.2x=81.6

1.2x÷1.2=81.6÷1.2

X=68

(9)x+5.6=9.4

X+5.6-5.6=9.4-5.6

X=3.8

(10)x-0.7x=3.6

0.3x=3.6

0.3x÷0.3=3.6÷0.3

X=12

(11)91÷x＝1.3

91÷x×x=1.3×x

1.3x=91

1.3x÷1.3=91÷1.3

X=70

(12)X+8.3=10.7

X+8.3-8.3=10.7-8.3

X=2.4

(13)15x＝3

15x÷15=3÷15

X=0.2

(14)3x－8＝16

3x-8+8=16+8