The number of red marbles in a jar is 3 times the number of blue marbles. There are 27 red marbles and b blue marbles. Write an equation to represent this situation. How many blue marbles are there?

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The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm