Answer:
40%
Explanation:
You subtract 11,970-8,550 = 3,420 to isolate the increase.
Divide 3,420/8,550 = .4 to get the percent increase of the markup.
The answer is .4 or 40% (they are equivalent)
You can check my work by multiplying 8,550 * .4 = 3,420
This answer is the percent of 8,550 that it increased (40% of 8,550) so make sure that is what the question is asking. If it is then it's your answer.