Taking the equation for this we can see that A is using 8 to multiply. 8% = 0.08. But since the percent is increases it would be 1.08. So we can see that it cant be A, this applys for B as well. For D it says 1.8 which is close but that would be 80% not 8%. So now we can see that C is the answer.
3x is the least common denominators because you need to be able to make sure all other denominators can go multiple into it. Since the rest are just x, the largest number of 3x would be the denominator you want.
