I´ve a page where I put the following calculations based on the price 1, tax 1 and tax 2. So you type the price, tax 1 and tax 2.
Then I´ve fields below that calculates the tax 1 cuota which is “price * tax 1” and tax 2 cuota which is “price * tax 2”, then the total which is “price + tax 1 cuota - tax 2 cuota” and I´m getting weird results.
For example: price = 1, tax 1 = 10 and tax 2 = 10. The app calculates the total = 19 € and it should be just 1 €
On your tax calculation, remove the number formatting. The decimal and comma separators might be messing things up.
also, as Nigel said above, Tax enter as 20% needs to be divided by 100.
You would be better to have custom states to hold all the raw numbers and do the calculations on, then present these in the UI using the number formatting options.