Word problem help plz!

Question

This is purely for me wanting to learn more math, this is not an assignment or test Q, I just want to improve my word problem ability, please help :(

 

A company currently sells 600 units of the product at a price of $20,000. Each unit costs $12,000 to produce. Based on its market research, it estimates that a 5% decrease in price will increase demand by 10%. What if the increase in demand is 15%?

Answer 1

Units (600 y) . . . Price ($20000 x)
. 1 . . . . . . . . . 1
. 1.1 . . . . . . . . 0.95
. 1.15 . . . . . . . .???

Use Point-Slope Form equation of a line:
y - 1 = ((1.1-1)/(0.95-1))(x - 1)

We want to know what x is if y = 1.15:

x - 1 = (1.15 - 1)*(-0.05)/0.1
x - 1 = (0.15)*(-5)/10
x = 1 - 0.15/2
x = 1 - 0.075
x = 1 - 7.5%

So a 7.5% decrease in price will increase demand by 15%.