3x-2=-2x+b
5x=b+2
x=(b+2)/5
-2x+b=0
-2x=-b
x=b/2
(b+2)/5=b/2
5b=2b+4
3b=4
b=4/3
уравнение
а) 2х-(6х+1)=9
2х-6х-1=9
-4х=10
х=-2,5
б) 4(1-5х)=9-3(6х-5)
4-20х=9-18х+15
-20х+18х=9+15-4
-2х=20
х=-10
в) 1,5(х-6)=1,4(х+5)
1,5х-9=1,4х+7
1,5х-1,4х=7+9
0,1х=16
х=160
(2 11/15 - 1 19/30) * 0,4 - 0,57 = - 0,13
1) 2 11/15 - 1 19/30 = 2 22/30 - 1 19/30 = 1 3/30 = 1 1/10 = 1,1
2) 1,1 * 0,4 = 0,44
3) 0,44 - 0,57 = - 0,13
0,43 + 0,3 * (1 5/12 - 9/20) = 0,72
1) 1 5/12 - 9/20 = 1 25/60 - 27/60 = 85/60 - 27/60 = 58/60 = 29/30
2) 0,3 * 29/30 = 3/10 * 29/30 = (1*29)/(10*10) = 29/100 = 0,29
3) 0,43 + 0,29 = 0,72
(11/35 - 4/21) : 3 7/15 + 3/5 = 89/140
1) 11/35 - 4/21 = 33/105 - 20/105 = 13/105
2) 13/105 : 3 7/15 = 13/105 : 52/15 = 13/105 * 15/52 = (1*1)/(7*4) = 1/28
3) 1/28 + 3/5 = 5/140 + 84/140 = 89/140