Question

Suppose a market research company finds that at a price of p = $30, they would sell x = 32 tiles each month. If they lower the price to p = $10, then more people would purchase the tile, and they can expect to sell x = 52 tiles in a month’s time. Find the equation of the line for the demand equation. Write your answer in the form p = mx + b. Hint: Write an equation using two points in the form (x,p).

Answer 1

OK remembering that (x,y) is (x,p) in this system (ie number of sales is the input, or independent variable and the price is the output {only a _bit_ confusing}.
you have 2 data points for the graph: (32,30) and (52,10)
1.) Find the slope = difference in p / difference in x = m
2.) find the intercept on p-axis (y-axis). Plug either coordinate pair into p=mx+b (you'll have "m" from step 1) to derive "b".
3.) Finally plug your "m" and "b" values into the generic slope-intercept equation: p=mx+b.
good luck.

Answer 2

http://www.purplemath.com/modules/strtlneq.htm
Half-way down if your struggling.