Remember this rule of thumb: two minus signs gives a plus sign. That knocks out the first hurdle - those nasty double minus signs:
Let's now rewrite both of these proper fractions as improper fractions:
Lastly, we need to set a common denominator. The best choice would be
See? We have the denominator we want, and at the same time, the fraction is still equal to the original value of
Now that we have a common denominator for both fractions, we can add them:
Since the problem was given with proper fractions, you will most likely want your answer to be a proper fraction too.