24* 80/100 = 24*8/10 = 19.2 is the answer.
I think very well that it is A or B. With my experience, but you might want to keep doing research.
Remember that you must change this number so that it is between 1 and 10, and then multiply it by a power of 10.
So first, you have to move the decimal point over 2 places to the right.
Since you are moving to the right, the exponent on ten will be negative; since you moved 2 decimal places, you know the exponent will be -2.
The answer is 6.3 x 10^-2.
Hope this helps!