D. 16.8 units
A radius is half of the diameter, so to get the answer all you need to do is multiply the length of the given radius by 2.
8.4x2= 16.8
The actual question is not visible
Let x be the number of cases of paper towels and y be the number of cases of soap. The system of linear equation that would best represent the given is,
x + y = 10
12x + 15y = 129
The values of x and y are 7 and 3.
Sarah both 7 cases of paper towel.
It is not possible for Sarah to buy exactly 20 bottles because first of all the cases contains only 12 bottles and 20 is not divisible by 12.