MATH PUZZLE: Can you replace...

Why the sun lightens our hair, but darkens our skin?
Why women can't put on mascara with their mouth closed?
Why you don't ever see the headline "Psychic Wins Lottery"?
Why "abbreviated" is such a long word?
Why doctors call what they do "practice"?
Why you have to click on "Start" to stop Windows XP?
Why lemon juice is made with artificial flavor, while dishwashing liquid is made with real lemons?
Why the man who invests all your money is called a broker?
Why there isn't mouse-flavored cat food?
Who tastes dog food when it has a "new & improved" flavor?
Why they sterilize the needle for lethal injections?
Why they don't make the whole plane out of the material used for the indestructible black box ?
Why sheep don't shrink when it rains?
Why they are called apartments when they are all stuck together?
If con is the opposite of pro, is Congress the opposite of progress?
Why they call the airport "the terminal" if flying is so safe?