Answer:
To find the percent markup, we can use the following formula:
Markup = (selling price - cost price) / cost price * 100
We know that the department store buys 100 shirts at a cost of $1,200 and sells them at a selling price of $20 each.
Markup = ($20 - $12) / $12 * 100
Markup = $8 / $12 * 100
Markup = 2/3 * 100
Markup = 67%
So the percent markup is 67%.