RO divides the rectangle into two congruent right triangles.
The area of the one triangle is equal half area of the rectangle.
Calculate the area of rectangle:

The area of right triangle:

Use the Pythagorean theorem to calculate the length of RO:

The formula of an area of this right triangle is:

Therefore we have the equation:

Not sure if your the same person but I had already done the work for this problem....
Answer:
8 (see work)
14. 2x^2 -4x^2 +3
Step-by-step explanation:
There's attached work for explanation
C, if you show a picture maybe I can answer it correctly