а) $$111000111_2 = 1*2^8 + 1*2^7 + 1*2^6 + 0*2^5 + 0*2^4 + 0*2^3 + 1*2^2 + 1*2^1 + 1*2^0 = 256 + 128 + 64 + 4 + 2 + 1 = 455_{10}$$
б) $$100011011_2 = 1*2^8 + 0*2^7 + 0*2^6 + 0*2^5 + 1*2^4 + 1*2^3 + 0*2^2 + 1*2^1 + 1*2^0 = 256 + 16 + 8 + 2 + 1 = 283_{10}$$
Ответ:
a) 455
б) 283