a) 23 + 16x = 31
16x = 31 - 23
16x = 8
x = 1/2
b) 3x - 14 = 9
3x = 9 + 14
3x = 23
x = 23/3
c) 2,5x + 5,6 = 12
2,5x = 12 - 5,6
2,5x = 32/5
x = 64/25
d) 5x + 1 = 2x + 19
5x - 2x = 19 - 1
3x = 18
x = 6
e) 8x + 3 = x + 15
8x - x = 15 - 3
7x = 12
x = 12/7
f) 7,8i - 8 = 1,3i + 2
7,8i - 1,3i = 2 + 8
6,5i = 10
x = 10/6,5
