Question 23594
When you subtract or add fractions you need to
have the same denominator in the fractions.
So you determine the "least common denominator"
be finding the smallest number into which the 
denominators you have can divide evenly.  That
number in your case is 16.
The 1st fraction already has that denominator so
you leave it alone.
For the 2nd fraction to have a denominator of 16 
you would have to multiply it by 2.  So you multiply
both top and bottom of that fraction by 2 to get 
the following:
 -7/16 - 6/16
Now you subtract the numerators and write the result
over 16 to get:
    -13/16.

Hope this helps.

Cheers,
Stan H.