Answer:
10%
Step-by-step explanation:
We have been given that the manager of a store orders model railroad sets that cost $390 and sells them for $429.
We will use markup % formula for our given problem.
[tex]\text{Markup percentage}=\frac{\text{Selling price- Cost}}{\text{Cost}}\times 100[/tex]
[tex]\text{Markup percentage}=\frac{429-390}{390}\times 100[/tex]
[tex]\text{Markup percentage}=\frac{39}{390}\times 100[/tex]
[tex]\text{Markup percentage}=\frac{1}{10}\times 100[/tex]
[tex]\text{Markup percentage}=10[/tex]
Therefore, markup is 10% of cost.