Answer: 7
Explanation:
To solve this problem you must apply the proccedure shown below:
1. You know that a multiplication has the following form:
a*b=c
Where a and b are the factors and c is the product.
2. You know one of the factor, then you can find the second one as following:
12*b=84
b=84/12
b=7
Therefore the answer is 7.