Answer:
12.5%
Explanation:
The price increased from 800 to 900. So what is the PERCENTAGE INCREASE??
The increase is 900 - 800 = 100
To find this in terms of original, we need to divide 100 by 800 and multiply by 100 to get the "percentage". Let's do it:

So the increase is 12.5% and thus the general sales tax is 12.5%