902 - x = 732 654+x=903 x + 257= 881
902 - x = 732
-х = 732 - 902
-х = - 170
х = 170
-------------------------
654 + x = 903
х = 903 - 654
х = 249
--------------------------
x + 257 = 881
х = 881 - 247
х = 634