Markup is the difference between a product's selling price and cost as a percentage of the cost.
If we call the cost of the dress as x, the markup is given by the following expression
[tex]markup=\frac{24-x}{x}\times100[/tex]The percent markup on the cost price of a dress is the same as the cost price in dollars, therefore, we can rewrite the previous expression as:
[tex]x=\frac{(24-x)\cdot100}{x}[/tex]Solving for x, we have:
[tex]\begin{gathered} x=\frac{(24-x)\cdot100}{x} \\ x^2=2400-100x \\ x^2+100x-2400=0 \\ \implies x=-120\:or\:x=20 \end{gathered}[/tex]Since we can't have a negative cost price, the markup is 20% and the cost price of the dress is $20.
