<span>Let x = the width
:
It says,"The length of a rectangle is 4 less than 3 times the width." write that as:
L = 3x - 4
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If the perimeter is 40, find the dimensions of the rectangle.
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We know: 2L + 2W = 40
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Substitute (3x-4) for L and x for W
2(3x-4) + 2x = 40
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6x - 8 + 2x = 40; Multiplied what's inside the brackets
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6x + 2x = 40 + 8; do some basic algebra to find x; (added 8 to both sides)
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8x = 48
:
x = 48/8
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x = 6 which is the width
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It said that L = 3x - 4, therefore:
L = 3(6) - 4
L = 18 - 4
L = 14; is the length
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Check our solutions in the perimeter:
2(14) + 2(6) =
28 + 12 = 40</span>
