
now, there are 1000 grams in one Kilogram, so in 1680 grams, there are 1680/1000 Kilograms, namely 1.680.
One line passes through the points (-2,3) and (0,-3) , it means the y intercept is b=-3
and slope m = 

So the equation of line will be 
And the inequality should be 
Or 
And the other line passes through (-2,3) and (0,2)
So the y intercept is b=2
and the slope is 
So the equation of line will be 
Or

So answer is 
Discount prices/the discount
E.g.the new price of the book is 75 which has a discount of 75%
The original price = 75/0.75=100