Answer:
Step-by-step explanation:
In
O, ST and VT are tangents at points S and V respectively.
In quadrilateral OSTV,
(By interior angle sum postulate of a quadrilateral)
(Measure of minor arc is equal to measure of its corresponding central angle)
(By arc sum property of a circle)

I hope this is what you're looking for. Sorry for my writing, I did it with the mouse lol.
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: