Reverse calculation help, please

[doro110011]

Hi. Can anyone help me with a reverse calculation of HST? I know that HST is ADDED at 13%, so a $100. invoice with total $113 with HST added.
But if I make a $100 PAYMENT on an invoice, how do I calculate how much of that payment is HST?

Any help appreciated.

 

[doro110011]

$\displaystyle Let\ price\ before\ HST = x.$

$\displaystyle And\ HST = 0.13x.$

$\displaystyle So\ price\ after\ HST = y = x + 0.13x = 1.13x.$ Follow that?

JeffM: Thank you for the answer, and also for how promptly you got it to me. I very much appreciate your help.

Thank you.

D.

 

[doro110011]

....thought you meant if $100 is applied to the $117 invoice...

Nope. JeffM understood exactly what I meant and was trying to accomplish.

Thank you though.

Best wishes.

D.