algebra help
posted by kelly .
(2,2) (4,20)
Find the value of x when y is 9.

I will assume you want
(2,2) , (x,9) , and (4,20) to lie on the same straight line?
if so,
method I : find the equation of the line using the two known points, then sub in y=9
Method II : just set up a ratio ...
(x+2)/(92) = (4+2)/(202)
(x+2)/7 = 1/3
3x + 6 = 7
x = 1/3 
how do you graph the function for p(x)=2x^2=12,500 where x is the number of items sold x(underscore)>3