7x÷15=2.13x-2(10-x)=152x-1.8=x+2.40.72×3+4x=3.06+3x7.8x-4x=2

①7x÷15=2.1
7x=2.1+15
7x=17.1
x=171/70
②3x-2(10-x)=15
3x-20+2x=15
5 x=15+20
x=7
③2x-1.8=x+2.4
2x-x=2.4+1.8
x=4.2
④0.72×3+4x=3.06+3x
2.15+4x=3.06+3x
x=3.06-2.15
x=0.91
⑤7.8x-4x=2x+3.6
1.8x=3.6
x=2
⑥3y+2+y-1+6y=10y+1

(1)x=0.3*15=4.5(2)5x=35,x=7(3)x=2.4+1.8=4.2(4)x=3.06-0.72*3=3.06-2.16=0.9(5)1.8x=3.6,x=2
(6)10y-1

(1)7x=31.5
x=4.5
(2)3x-20+2x=15
5x-20=15
5x=35
x=7
(3)x=4.2(直接写）
(4)2.16+4x=3.06+3x
x=5.22
(5)3.8x=2x+3.6

1. 7x=2.1*15 x=2.1*15/7

2. 3x-20+2x=15 5x=15+20 x=35/5=7

3. x=2.4+1.8

4. x=3.06-(0.72*3)

5. 1.8x=3.6 x=2

7x÷15＝2.1
7x＝2.1×15
x＝4.5
3x－2（10-x）＝15
3x－20+2x＝15
5x＝35
x＝7
2x－1.8＝x＋2.4
2x－x＝2.4+1.8
x＝4.2
0.72×3+4x＝3.06+3x
4x－3x＝3.06-2.16
x＝0.9
7.8x－4x＝2x＋3.6...

4.5 7 4.2 0.9 2 10y+1

⑴4.5 ⑵7 ⑶4.2 ⑷0.9 ⑸2 ⑹0y+1

x=2.1*15/7
x=4.5
解 3x-20+2x=15
5x=35
x=7
解 x=2.4+1.8
x=4.2
解 x=3.06-3*0.72
x=3*(1.02-0.72)=0.9
解 1.8x=3.6
x=2
最后一题不是方程。。谢谢~