Answer: Percent of people who had a mild allergic is 0.6%.
Explanation:
Since we have given that
Total number of people try a new shampoo = 7000
Number of people had a mild allergic reaction = 42
We need to find the "Percentage of people had a mild allergic":
Percentage of people had a mild allergic is given by

Hence, Percent of people who had a mild allergic is 0.6%.