Multiply 6 by 9 (whole number by denominator)
then add that to 15 (the product to the numerator.
Please show the entire question. What are you trying to do with these problems?
Answer:
Well, it's the perimeter, so...40.
You just calculate the perimeter of a rectangle with the lenght of 12 and width of 8, by the formula

or you can factor it out.