18.2
1) 4x = -20
x = -20 : 4
x = -5
2) 3y + 2y - 2y = 9
3y = 9
y = 9 : 3
y = 3
3) 4x = 12
x = 12 : 3
x = 4
4) 4z - 3z = -1
z = -1
5) y = 1,6 : 2
y = 0,8
6) z+2 = 8
z = 6
7) -x = 6,2
x = -6,2
8) 3z = 0
z = 0
9) x = 0,7 * 3
x = 2,1
18.3
1) 3x = 6
x = 2
2) 5z = -6
z = -1,2
4) 4x = 8
x = 2
5) 5y - 4y = -8
y = -8
7) 3z + z = -8
4z = -8
z = -2
8) x + 9x = -1
10x = -1
x = -0,1