ok so
8000=cost
profit-8000
then
another cost is 15rand per mug
but profit of 35 rand
35-15=20
profit of 20rand per mug
profit=R20m-R8000
where m=number of mugs sold
(R20 means 20 rand)
f(m)=R20m-R8000
break even means cost=earned
basically, when profit=0
0=R20m-R8000
add 8000 to both sides
R8000=R20m
divide both sides by 20
400=m
break even is 400 mugs
graph should be easy enough
put a point at (0,-8000) and at (400,0) then connect them
profit
f(x)=R20x-R8000
break even is 400 mugs
put points (0,-8000) and (400,0) and connect them