Answer:
When b = 28 and c = 4, then a = 56
Explanation:
We need to write the equation first
This is an example of a combined variation
if a varies directly as b and inversely as c;
then a = bk/c
where k is the constant of proportionality
We find k first;
16 = (12 * k)/6
k = (6 * 16)/12 = 8
We now want to find a
a = kb/c
a = (8 * 28)/4 = 7 * 8 = 56