C. Is try correct answer
See example in the attached picture
Answer:
#4. m=0;
#3. m = 
Step-by-step explanation:
It seems right.
#4.
Maybe your teacher wants you to write m=0; because when a fraction has a numerator equal to zero then the fraction is zero.
#3.
Maybe your teachers want you to simplify the fraction and write m = 
5b + r = 30
the cost per item * the number of items sold = the profit
Here is a video:
Website:
1. https://www.khanacademy.org/math/pre-algebra/pre-algebra-fractions/pre-algebra-div-fractions-word-problems/v/dividing-a-fraction-by-a-whole-number-word-problem
2. https://www.khanacademy.org/math/arithmetic/fraction-arithmetic/arith-review-dividing-fractions/v/dividing-fractions-example