Jennifer and Marci are selling cookies for a fundraiser. They sold 28 boxes of cookies together. Marci sold 5 less than twice the number that Jennifer sold. How many boxes of cookies did each girl sell? Use system of equations to solve the problem ( y=2x-5)
Let's assume that Jennifer sold x boxes of cookies.
According to the problem, Marci sold 5 less than twice the number that Jennifer sold, which is 2x - 5.
The total number of boxes they sold is 28, so we can set up the equation x + (2x - 5) = 28.
Combining like terms, we get 3x - 5 = 28.
Adding 5 to both sides, we get 3x = 33.
Dividing both sides by 3, we get x = 11.
So, Jennifer sold 11 boxes of cookies.
Substituting x = 11 into the equation y = 2x - 5, we get y = 2*11 - 5 = 22 - 5 = 17.
Therefore, Marci sold 17 boxes of cookies.
Jennifer sold 11 boxes of cookies and Marci sold 17 boxes of cookies. Answer: \boxed{11, 17}.