Answer: 4/5
Step-by-step explanation: Using the place value chart, we can see that 0.8 is eight-tenths, so we can write 0.8 as the fraction 8/10. Notice however that 8/10 is not in lowest terms so we need to divide the numerator and the denominator by the greatest common factor of 8 and 10 which is 2. If we divide the numerator and the denominator by 2 we will get 4/5.
Therefore, 0.8 can be written as the fraction 4/5.