There is not much that can be done to figure out how to write 0.81 as a fraction, except to literally use what the decimal portion of your number, the .81, means.
Since there are 2 digits in 81, the very last digit is the "100th" decimal place.
So we can just say that .81 is the same as 81/100.
So your final answer is: 0.81 can be written as the fraction 81/100
