We can convert 20km to 20,000m. Then, we can subtract 800m (walking distance) from 20,000m which would result in 19,200m. Then we can put 19,200m and 20,000m as a fraction (19200/20000). Before we can multiply it by 100 to make it in the percentage form, we can get rid of 2 zeroes for both number making it 192/200 and then further simplifying it to 24/25 by dividing both numbers by 8. Finally to get the percentage we can multiply 24 and 100 (2400) and then divide the result (2400) by 25. The final answer is 2400/25=96 meaning he cycled 96% of the journey and walked 4% of the journey (100-96=4).
