Is this correct?? If no what are the correct answers??? Please show your work. Thanks!

Computers work in a base 2, or 'binary' system. That is, the computer uses only two digits: O and 1 (that are represented by "on" and "off"). The largest 4-bit binary number is 1111 -15, the largest 8-bit number is 1111 1111, and so on. Assuming that coding starts at zero (e.g., 00000), supply the largest numbers represented in an 8-bit system 12-bit system 111111111111, and 16-bit system 1111111111111(Enter an integer number - no decimal)