If the area of the table is 36 inches by 24 inches, will they have enough tiles to cover the table? if not, how many more will they need?

it would be 6xy and -16xy.

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents