I believe the term is "constant".
OK so first I like to find what 10% is which in this case would be 1.8 and to find the other 5% you divide 1.8 by 2 which gets you .9 if you and 1.8 and .9 you get 2.7 and if you add 2.7 to 18 you get 20.7 which is your retail price
Yes because the general form of a power function is f(x)=cx^p, where c and p are real numbers. Since the function satisfies this form, the function is a power function.
This is a difference of perfect square so you get (2x+6)(2x-6)=0, solving will give you 3,-3
7-2/3x<x-8
add 2/3x to both sides
7<5/3x-8
add 8 to both sides
15<5/3x
times 3 both sides
45<5x
divide both sides by 5
9<x