PETE C. answered 03/04/20
Taught high school Algebra I & II three years and SAT MATH PREP 2 yrs
Let W = width in inches
Let L = length in inches
PERIMETER = 30 inches
2W + 2L = 30
AREA = 56 SQUARE INCHES
LW = 56
L = 56/W
Substituting 56/W into the equation 2W + 2L = 30.
2W + (2)(56/W) = 30
2W + (112/W) = 30
2W^2 + 112 = 30W Multiply entire equation by "W".
2W^2 - 30W + 112 = 0
W^2 - 15W + 56 = 0 Divide entire equation by 2. Some say multiply by 1/2. Same thing.
(W - 8) (W - 7) = 0
So, W = 8 FT OR W = 7 FT
Since the WIDTH is always shorter than the LENGTH, the WIDTH IS 7 INCHES.
The longer measurement, 8 INCHES IS THE LENGTH.
CHECKING:
AREA 7 in X 8 in = 56 sq in
PERIMETER = 2W + 2L = (2)(7) + (2)(8) = 14 in + 16 in = 30 in
Hope this helps you TA.