Answer:
A
Step-by-step explanation:
360 ÷ 12 = 30.
The measure of an interior angle of a dodecagon is 30°. (:
Markup means they sell it for that percentage more than they bought it for. First let's calculate how much they will mark it up for:

Convert 87% into a decimal(87/100):

Multiply:

This is how much they'll mark it up, now let's add it to how much they bought it for to find out the selling price:
Use m=y2-y1/x2-x1 when you find the slope of two coordinates :)