Answer:
25%
Explanation:
The cost for one shirt is ...
$3200/(400 shirts) = $8/shirt
The equation for markup is ...
selling price = cost(1 +markup fraction)
Solving for the markup, we find ...
markup fraction = (selling price)/cost -1
= 10/8 -1 = 2/8 = 1/4 = 25%
The markup is 25%.