Well, first we can rule out B and D. When you multiply a positive number by a negative number, you will get a negative number. Since the product of this equation is a positive, we can rule these 2 out. Now we are left with A and C. There are 2 ways you can solve this. You can divide 144 by 16 or 36, or multiply 4 by 16 or 36. I perfer to multiply 4 by A or C. 4 x 16 = 64. So we can rule that one out. SO your answer is C.