Din formula suma mezilor = suma extremilor rezulta
27. 3 ori 15 = 5(3x - 2)
45 = 5(3x - 2)
9 = 3x - 2
3x = 11
x = 11/3
28. 4(5 - 2x) = 10
2(5 - 2x) = 5
10 - 4x = 5
4x = 5
x = 5/4
29. 6 = 4(3 + 5x)
3 = 2(3 + 5x)
3 = 6 + 10x
10x = -3
x = -3/10
30. (6x - 11)5 = 42
30x - 55 = 42
30x = 97
x = 97/30
