Bucks, Good afternoon.
Issues involving taxes are always complicated to understand.
This happens anywhere in the world.
Accept then, is an almost impossible thing.
ha ha ha
That's my opinion.
Returning to the main issue ...
If taxes are within the price so you do not have 100% of their price only.
You have 100% of their price
PLUS taxes.
In your case over 30%.
Therefore, its price is
130%.
So $10.00 is 130%
therefore:
10% of the price is $0.77
20% of the price is $1.54
Your actual price is $7.69
The formulas:
A1 = 10
B1 --> tax --> 30%
C1 --> TAX --> =A1/13*3
D1 --> Your REAL Price --> =A1-C1
Then...
TAX 10% --> =A1/13
TAX 20% --> =A1/13*2
Compoundig Final PRICE:
D1 --> Your price =$7.69
D2 --> Tax =30%
c3 --> FINAL price --> =D1*(1+D2)
Is that what you're looking for?
I hope it helps.
--
Belo Horizonte, Brasil.
Marcílio Lobão