You may have tried to combine all the terms, but they are not all like terms. Distribute the subtraction sign to both terms in the subtrahend.

$\displaystyle{9}-{\left(-{2}-{6}{i}\right)}={9}+{2}+{6}{i}\usepackage{cmbright}\Huge\$

Rearrange the terms to put like terms together, and then combine like terms.