Çözüldü Trapezoid Perimeter - Pythagorean Theorem (To be mentally solved)

https://i72.servimg.com/u/f72/19/97/10/39/trapez10.png
Top 50 SAT Math Skills
http://library.lol/main/D9C4B8E57A06080297263B98426A16F3
[ Page 4 (15 in the pdf file), Question 21, Pre-test Answers on page 135 (146 in the pdf file) ]

3 + 3·6 + (3^2 + 6^2)^0.5 = 21 + √45 = 21 + 3·√5 units <=== Must be done within a few seconds in the mind only.