First, eliminate C and D.
P = CO * VR,
We doubled the left side of the equation (increased it by 100%), but we didn't double the right side (almost there, but we only increased it by 50%). So we need to increase CO to make it true.
So what number do we have to increase CO by to get the right side of the equation to also double?
For choice A, we are increasing it by 33% which is the same as multiplying by 1.33 or 4/3. So 4/3 * 3/2 = 12/6 = 2. So A is the right answer.
Choice B is increasing by 50% or multiplying by 3/2. 3/2 * 3/2 = 9/2 = 4.5 which is way too much.
FYI: You should know that an increase of 10% means multiplying that number by 1.10. A decrease in 10% is like multiplying that number by 0.90. Don't get this terminology/convention confused.
