Alright, lets get started.
The cost of model train = $ 50 (given in question)
markup percentage is given = 30 %
Markup price is asked.
The formula for markup price = cost + cost * markup percent
Hence , the markup price = 50 + 50 * 30%
The markup price = 50 + 50 * 0.3
The markup price = 50 + 15
The markup price = 65 $ : Answer
Hope it will help :)
