Move the decimal so there is one non-zero digit to the left of the decimal point. The number of decimal places you move will be the exponent on the 10. If the decimal is being moved to the right, the exponent will be negative. If the decimal is being moved to the left, the exponent will be positive. So you will not have a negative exponent, because the decimal is moved to the left not the right it will actually be a +6 exponent. Also you only get a negative exponent if it is a small number like .56789 then you'd have a negative exponent, but that is not the case for this problem.
If you divide the number of serves in by 2 ( number that he lands in for every 6 serves) and then multiply by 4 ( number that land out for every 6 serves), you get 52 serves out.
