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when the length of a rectangle is X inches and the width is y inches, the perimeter is 30 inches. if the length is tripled and the width is quadrupled the perimeter becomes 102 inches. find the length and width of the original rectangle

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dannielle

P1=2x+2y=30

after modify them

P2=2*3x+2*4y=102

     6x+8y=102

      2x+2y=30      / * (-3)

      -6x-6y= -90

       6x+8y=102

we must add the 2 expressions

         / 8y-6y=102-90

            2y=12

           y=12:2

          y=6

       2*x+2*y=30

       2x+2*6=30

       2x+12=30

      2x=30-12

     2x=18

      x=18:2

      x=9