123 + x + ( 1 + 99 ) = 323
123 + x + 100 = 323
123 + x = 323 - 100
123 + x = 223
x = 223 - 123
x = 100
123 + x + ( 1 + 99 ) = 323
123 + x + 100 = 323
123 + x = 323 - 100
123 + x = 223
x = 223 - 123
x = 100
nha bn
=123+x+100=323
=(123+100)+x=323
=223+x=323
x=323-223
x=100