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Answer:
w = 7 cm.
Explanation:
Given:
P = 56
Use the formula P = 2l + 2w to solve for the perimeter of the rectangle.
Let w = width, and
3w = length
Plug these into the equation:
56 = 2(3w) + 2(w)
56 = 6w + 2w
Combine like terms:
56 = 8w
Divide both sides by 8:
w = 7 cm.
The width of rectangle is 7 cm.