(70+30)+600=700
500-(600-200)=100
(200+200)+(300-100)=600
(200-100)+300=400
1000-(500+100)=400
800-(600-100)=300
900-(600-300)=600
(400+500)-100=800
1) 6х - (х - 1) = 2(2х - 4)
6х - х + 1 = 4х - 8
5х - 4х = - 8 - 1
<h3>х = - 9</h3>
- - - - - - - - - - - -
2) 3(2х - 5) = 7х + 11
6х - 15 = 7х + 11
6х - 7х = 11 + 15
- х = 26
<h3>х = - 26</h3>
- - - - - - - - - - - -
3) 3(2х - 5) = 7х + 1
6х - 15 = 7х + 1
6х - 7х = 1 + 15
- х = 16
<h3>х = - 16</h3>
<span>12=4*3, а 15=5*3;
21=3*7, а 35=5*7.
Получится: (4*3*3*7)/(5*7*5*3)=(4*3)*(3*7)/(5*5)*(3*7)=12/25</span>