Applying a markup of $n$% to a base amount is the same as multiplying the base amount by $$\frac{100 + n}{100}$$ To remove the markup, just multiply the marked up amount by $$\frac{100}{100+n}$$
Applying a markup of $n$% to a base amount is the same as multiplying the base amount by $$\frac{100 + n}{100}$$ To remove the markup, just multiply the marked up amount by $$\frac{100}{100+n}$$