The answer is 90, Because angle D is a 90 degree angle, and 180- 90=90, so the answer is 90.
We use the formula a^2 - b^2 = ( a - b )( a + b );
We have a = 5m - 2 and b = 3m - 4;
<span>(5m-2)^2-(3m-4)^2 = (5m - 2 -3m + 4) x (5m-2 + 3m - 4) = (2m + 2)(8m - 6) = 2(m +1) x 2(4m - 3) = 4(m+1)(4m-3);
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The bottom rectangle is 52 ft by 27 ft.
The top rectangle is 30 ft by 17 ft (calculated as 57 ft - 27 ft - 13 ft = 17 ft).
The connector rectangle is 13 ft by 9 ft (calculated as 30 ft - 21 ft = 9 ft).
total area = 52 ft * 27 ft + 30 ft * 17 ft + 13 ft * 9 ft
total area = 1404 ft^2 + 510 ft^2 + 117 ft^2
total area = 2031 ft^2
weight = 2031 ft^2 * 12 lb/ft^2
weight = 24,372 lb

means you shade the part above the line, and

means you shade the part under the line.
If it has an equal bar under it, like this:

, then you also shade the line, by making it solid instead of dotting it.