5x - 5x + 1 + 5x + 2 = 3900 - 5x + 3
=> 5x - 5x . 5 + 5x . 52 = 3900 - 5x. 53
=> 5x - 5x . 5 + 5x . 25 = 3900 - 5x. 125
=> 5x . 125 + 5x - 5x . 5 + 5x . 25 = 3900
=> 5x.(125 + 1 - 5 + 25) = 3900
=> 5x. 146 = 3900
=> 5x = 3900 : 146
=> 5x = 1950/73
=> \(x\in\varnothing\)