From the given options 64 units are the area of the square that Margo used. So, option D is correct.
SOLUTION:
Given, Margo draws a triangle. The lengths of the sides of the triangle are
Margo uses the area of 3 squares to show that the triangle is a right triangle. We have to find the area, in square units, of a square that Margo uses. Now, we know that we can prove a triangle as right angled triangle using Pythagoras' theorem
Assume that the above theorem is the equation of the area of one square = sum area of two squares. Then, using the area of three squares we can prove that a triangle is a right-angle triangle.
Now, areas of the three squares will be