3. Look at the picture.
Use Pythagorean theorem:
[tex]x^2=3.6^2+5.5^2\\\\x^2=12.96+30.25\\\\x^2=43.21\to x=\sqrt{43.21}\\\\\boxed{x\approx6.6}[/tex]
4.
Use Pythagorean theorem:
[tex]3^2+\left(\dfrac{x}{2}\right)^2=6.5^2\\\\9+\dfrac{x^2}{4}=42.25\ \ \ |-9\\\\\dfrac{x^2}{4}=33.25\ \ \ \ |\cdot4\\\\x^2=133\to x=\sqrt{133}\\\\\boxed{x\approx11.5}[/tex]
5.
[tex]\widehat{AB}\ \cong\ \widehat{DE}[/tex]
