Odpowiedź:
a)
10a + 5 = 5a + 20
10a - 5a = 20 - 5
5a = 15 | :5
a = 3
b)
2x - 2(x + 5) = x - 8
2x - 2x - 10 = x - 8
-x = (-8) + 10
-x = 2 | * (-1)
x = -2
c)
5 (x - 1) - 4 (x + 3) - 5 = 3 (x - 2)
5x - 1 - (4x + 12) - 5 = 3x - 6
5x - 1 -4x - 12 - 5 = 3x - 6
5x - 4x - 3x = 1 + 12 + 5 - 6
-2x = 12 | : (-2)
x = 6
d)
4 - [2 - 5(x + 1)] = 2 * 19 - 2x - 11 + 4
4 - [2 -5x - 5] = 38 - 2x - 11 + 4
4 - 2 + 5x + 5 = 38 - 2x - 11 + 4
5x + 2x = 38 - 11 + 4 - 4 + 2 - 5
7x = 27 - 3
7x = 24 |:7
x = 3 i 3/7