Answer:
Arithmetic
Step-by-step explanation:
Answer is 12.73
Use Pythagorean theory
Split square into two right triangles with diagonal line. To find the diagonal
a^2 + b^2 = c^2
9^2 + 9^2 = c^2
162= c^2
Take square root of both sides
12.73 = c
Line DE is 4 squares and Line BC is 8 squares.
The length of line DE is 1/2 of line BC