suppose a market research company finds that a price of p=$22, they would sell x=42 tiles each month. If they lower the price to p=$12, then they would purchase the tile and they can expect to sell x=52 tiles in a month. Find the equation of the line for the demand equation. write the answer in the form of p=mx+b. write an equation using two points in the form(x,p)

The instructions appear quite explicit

so you have two ordered pairs
(42,22) and (52,12)
slope = (12-22)/(52-42) = -10 / 10 = -1
so p = -x + b
sub in one of the points, say (42,22)
22 = -42 + b
b = 64

p = -x + 64

test with the above point not used, that is , (52,12)
LS = 12
RS = -52 + 64 = 12
all is good!