Formula for calculating transaction fees Let's say a credit card processor wants to charge $(3\% + \text{US}\$ 2)$ for all transaction.
What formula do I use to make sure that after the charges are deducted, I get the figure I want.
Example: If my product is $\text{US}\$ 100$  How much do I need to increase the price so that I will get $\text{US} \$100$ even after the transaction is charges by the credit card processor.
If it is purely $\% $-based, then I believe it is $\dfrac{\text{US}\$100}{1-0.03}$. But with the $\text{US}\$2$ in play, I am not sure how to do it. Please help :)
 A: Let $x$ be the price we charge. Then there is a transaction fee of $3$ percent, that is $0.03x$. There is an additional charge of $2$ dollars. 
So we end up with a net amount of $x-0.03x-2$. We want this to be (say) $100$.
Thus 
$$x-0.03x-2=100.$$
Simplify this first to $x-0.03x=102$, then to $0.97x=102$. We find that $$x=\dfrac{102}{0.97}.$$ 
A: $100=(1-\frac{p}{100})x-2$ so $$x=\frac{102}{1-\frac{p}{100}}$$
To account for the $2$ dollar surcharge, you can think of the price of the item as being $102$ with surcharge, then apply what you have already figured out.
A: Okay just for my understanding, for \$100, they will charge you 3% (=\$3) + \$2 so you are finally left with \$95? If that is the case I understood your question correct.
Let us assume you are at an ATM and click the "\$X" option. What you get is not \$X, but 
$\$X \cdot(100\%-3\%)-\$2$ so you are left with $\$X\cdot0.97-\$2 $. If you actually want to have \$100 after they charged you, you want  $\$X\cdot0.97-\$2 $ to equal \$100.
So you have to solve $\$X\cdot0.97-\$2  = \$100 $ for $\$X$. The results in 
$$ \$X = \$102/0.97\approx \$105.15 $$
