Here’s what you can do to make this very simple. Consider that the “missing” space between the rectangles isn’t there. Then, find the area:
10 x 9 = 90 mm
Now, find the area of the “missing” part.
5 x 2 = 10 mm
Finally, you deduct the missing part from the complete rectangle!
90 - 10 = 80 mm
The area of this whole thing is 80 mm!
Use Pythagorean thrm
17^2+10^2=21^2
289+100=441
389≠441
This is not a right triangle
First step, divide 6 from both sides.
t/6=r^2+1
second step, subtract 1 from both sides
t/6 -1=r^2
Now take the square root of each side.

Done!
Answer:
C , 18
Step-by-step explanation: