Hello from MrBillDoesMath!
Answer:
-9 sqrt(5)
Discussion:
-2 sqrt(20) - sqrt(125) =
-2 *2 sqrt(5) - sqrt(125)= as 20 = 4* 5
-4sqrt(5)- 5 sqrt(5) = as 125 = 25 *5
(-4 -5) sqrt(5) =
-9 sqrt(5)
Thank you,
MrB
For #31 you would make two squares on the left and right side and then four rectangles in the middle