Explain how to use a pattern to find the product of a power of 10 and a decimal

for a power of ten all you need is just add a zero, example, 10 to the power of 10 just add ten zeros behind the 10 > 100,000,000,000

the answer is 99.

this may not be at all, but i use the same website you're using for school, and if i'm stuck doing one of these i try to look for it on the section.