1)-2х+3=0
-2x = -3
x = -3 : (-2)
x = 1,5
2)-4х+3=2х
-4x -2x = -3
-6x = -3
x = -3 : (-6)
x = 3/6
3)6-5х=2х-1
-5x -2x = -1 -6
-7x = -7
x = -7 : (-7)
x = 1
4)4(3-х)=х+7
12 - 4x = x + 7
-4x -x = 7 -12
-5x = -5
x = -5 : (-5)
x = 1
5)7-3(2х+1)
7 = 6x + 3
- 6x = 3 -7
-6x = -4
x = -4 : (-6)
x = 4/6
6)-3х-2=7
-3x = 7 + 2
-3x = 9
x = 9 : (-3)
x = -3
7)4х+3=2х
4x -2x = -3
2x = -3
x = -3 : 2
x = -1,5
8)6-5х=-2х+9
-5x + 2x = 9 -6
-3x = 3
x = 3: (-3)
x = -1
9)2(х+1)=3
2x + 2 = 3
2x = 3 - 2
2x = 1
x = 1 : 2
x = 1/2
10)9-2(3-4х)=-2х+1
9 -6 + 8x = -2x + 1
8x + 2x = 1 - 3
10x = -2
x = -2 : 10
x = -2/10
P.s. / – это дробь
1,2 * (21 + 9х) = 18 + 12х
25,2 + 10,8х = 18 + 12х
25,2 - 18 = 12х - 10,8х
7,2 = 1,2х
х = 7,2 : 1,2
х = 6
ответ: через 6 дней.
Проверка:
1,2 * (21 + 9 * 6) = 18 + 12 * 6
1,2 * 75 = 18 + 72
90 = 90