a) i) 3x-6y=24 can be reduced to x-2y=8, 2y=x-8, y=½x-4, which has a slope ½ as does every parallel line.

ii) Perpendicular slope is -2 (-1/½)

iii) y=5 is parallel to the x-axis and all x values are on this line

b) Linear relation y=mx+a where m is the slope and a is a constant. m=(75000-45000)/(2000-1000)=30000/1000=30. a) coords are (1000,45000) and (2000,75000).

Using slope-intercept:

y-45000=30(x-1000), y=30x-30000+45000=30x+15000. Note that when x=2000, y=75000 which confirms the equation as correct:

b) y=30x+15000 where y is revenue in Rs and x is the number of books.