1. 2x – 3y = 12.....all we have to do is solve for y, i guess you could graph the line just for fun.

=> -3y = 12 - 2x .........subtracted 2x from both sides

=> y = (2/3)x - 4 .........divided both sides by -3. this looks familiar, didn't topsquark do this already?

2. (a)

we just plug in the values in the formula given:

=> the cost equation is:

C = 10x + 40

(b) Graph the cost equation.

obviously, the cost equation gives the graph of a straight line, so all we need are two points (if you want to plot more you can). we already know the y-intercept, it's the lone constant 40. so one point is (0,40). now let's find the x-intercept:

for x-intercept: y = 0 (or in this case, C = 0)

=> 0 = 10x + 40

=> -40 = 10x ...........subtracted 40 from both sides

=> -4 = x ...........divided both sides by -10

so the x-intercept is (-4,0)

so now we draw our axis and plot those points: