a, 315 + (146 – x) = 401
ó 146 – x = 401 – 315
ó146 – x = 86
ó x = 146 – 86
ó x = 60
b, (x + 251) – 301 = 56
ó x + 251 = 56 + 301
ó x = 357 – 251
ó x = 106
c, (x – 29) – 11 = 0
ó x – 29 = 11
ó x = 11 + 29
ó x = 40
d, 103 – (x – 34) = 61
ó x – 34 = 103 – 6
ó x = 97 + 34
ó x = 13