Turn the 6 into a fraction. It is easiest to put the 6 over 1. (This does not change the value of the 6.) Then you want common denominators. (The bottom number of the fractions to be the same.) When adding fractions, you only add the top numbers and the bottom stays the same. Simplify the fraction to 5 1/2 or 5.5
$${\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{6}}}{{\mathtt{1}}}}\right) = {\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{12}}}{{\mathtt{2}}}}\right) = {\frac{\left({\mathtt{\,-\,}}{\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{12}}\right)}{{\mathtt{2}}}} = {\frac{{\mathtt{11}}}{{\mathtt{2}}}} = {\mathtt{5.5}}$$
Another way is to turn the problem around to 6-1/2
1/2 of 1 is .5
$${\mathtt{6}}{\mathtt{\,-\,}}{\mathtt{0.5}} = {\mathtt{5.5}}$$
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