Convert $+12$ and $+9$ to binary, using the signed$-2\text{'}$s$-$complement representation and enough digits to accomodate bers. Then perform the binary equivalent of:

$($a$)(-12)+(+9)$

$($b$)(-12)-(-9)$

You do not need to convert the aswers back to decimal, leave them in signed$-2\text{'}$s$-$complement binary representation.