(456 + 112) - x = 400
x - (203 + 303) = 34
(283 - x) - 33 = 0
382 - (x + 42) = 111
(536 + x) - 420 = 116
437 - (227 + x) = 0
468 - 217 - x = 51

1. (456 + 112) - x = 400  

568 - х = 400

х = 568 - 400

х = 168

2. x - (203 + 303) = 34

х - 506 = 34

х = 506 + 34

х = 540

3. (283 - x) - 33 = 0  

283 - х = 0 + 33

283 - х = 33

х = 283 - 33

х = 250

4. (536 + x) - 420 = 116

536 + х = 116 + 420

536 + х = 536

х = 536 - 536

х = 0

5. 437 - (227 + x) = 0  

227 + х = 437 - 0

227 + х = 437

х = 437 - 227

х = 210

6. 468 - 217 - x = 51  

251 - х = 51

х = 251 - 51

х = 200