Hey there!!
Total cost - 800
This cost is included with the 20% VAT .
Let's take the original price as 'x'.
Then,
Sum of 20% of 'x' and x would be 800.
... 20x/100 + x = 800
... x/5 + x = 800
... 6x/5 = 800
... 6x = 800 * 5
... 6x = 4000
... x = 666.666667.
Hence, the original price is 666.67 ( avg ).
Hope my answer helps!!