Answer:
the answer is 7 candy bars
Explanation:
theres two ways of doing this the equation way and the common sense way m(x) basically just means y so y= 3x -20 we can set y to 0 so 0 = 3x -20 next add 20 to the other side 20 = 3x then divide both sides by 3 you get x= 6.666 but you cant sell .666 of a chocolate bar so round to 7 and thats your answer. the other strategy is saying hey i get $3 per candy bar what number would put be at 21 since 21-20= $1 and we say 7*3 = 21 so 7 is the answer.