Question

C2/d at c = 6, d =3

Answer 1

If the C2 is referring to C^2 (c squared), then 

C^2 = 6^2 = 6*6 = 36
Note how I replaced the "C" with 6, because C = 6
Squaring a number is the same as multiplying it by itself. 

Once you know the value of C^2, you divide it over the value for d, which is 3

So,
(C^2)/d = (36)/3 = 12

The final answer is 12

Answer 2

If C=6 and D=3, then C times 2 equals 12.
12 divided by 3 equals 4.
so your final answer would be 4.