a) 7 - 28 = 5x + 2x
-21 = 7x /7
-3 = x
x = -3
spr.
7 - 2*-3 = 5*-3 + 28
7 - (-6) = -15 + 28
13 = 13
b)
8x - 15 = 2x - 3
8x - 2x = 15 - 3
6x = 12 /:6
x = 2
spr.
5*2 + 3*2 - 15 = 2*2 - 3
10 + 6 - 15 = 4 - 3
16 - 15 = 1
1 = 1
c)
8x - 3x = 12 - 17
5x = -5 /:5
x = -1
spr.
8*(-1) - 12 = 3*(-1) - 17
-8 - 12 = -3 - 17
-20 = -20
d)
8x - 3x = 5 + 10
5x = 15 /:5
x = 3
spr.
6*3 + 2*3 - 10 = 3*3 + 5
18 + 6 - 10 = 9 + 5
24 - 10 = 14
14 = 14
