Ответ:

А) \(1011001_2=89_{10}\), \(10101_2=21_{10}\); \(89-21=68=1000100_2\).

Б) \(101001_2=41_{10}\), \(100100_2=36_{10}\); \(41+36=77=1001101_2\).

В) \(120_8=80_{10}\), \(113_8=75_{10}\); \(80-75=5=5_8\).

Г) \(18_{16}=24_{10}\), \(A3_{16}=163_{10}\); \(24+163=187=BB_{16}\).