Final answer:
Wang Yong paid back a fixed amount of $170 each month.
Step-by-step explanation:
To find the fixed amount Wang Yong paid back each month, we subtract the remaining debt from the initial debt and divide it by the number of months. In this case, Wang Yong owed $8500 and after 12 months, his remaining debt was $6460. Therefore, the fixed amount he paid back each month is:
Fixed amount = (Initial debt - Remaining debt) / Number of months
Fixed amount = ($8500 - $6460) / 12
Fixed amount = $2040 / 12
Fixed amount = $170
Therefore, Wang Yong paid back $170 each month.