49 - [4275:19 + (24 × 54 - 34x) : 12] = 30
49 - [225 + (1296 - 34x) : 12] = 30
49 - 225 - (1296 - 34x) : 12 = 30 |·12
588 - 2700 - (1296 - 34x) = 360
588 - 2700 - 1296 + 34x = 360
588 + 34x = 360 + 2700 + 1296
588 + 34x = 4356
34x = 4356 - 588
34x = 3768 |:2
17x = 1884
x = 1884:17