Question

de - ab = ___ ft.
options: 10, 18, 8

Explanation:

Step1: Find length of AB

$\triangle ACB$ is right triangle, use Pythagoras:
$$AB = \sqrt{AC^2 + BC^2} = \sqrt{6^2 + 8^2} = \sqrt{36+64} = \sqrt{100} = 10 \text{ ft}$$

Step2: Identify length of DE

From diagram, $DE = 20 \text{ ft}$

Step3: Calculate DE - AB

$$DE - AB = 20 - 10 = 10 \text{ ft}$$

Answer:

10