What is the length of side s of the square shown below?

C. units.

Step-by-step explanation:

From the given figure , a square is shown with diagonal 8 units.

To find : the length of side (s) of the square .

In a square : All four sides are equal in length and all four angles are right angles.

Thus, The diagonal(hypotenuse) is making two right -angled triangle with the sides of square.

So by Pythagoras theorem of right triangles , we have

Hence, the length of side s of the square= units.

So the exterior angle of any polygons are 360 in total. since in the pic there r some interior angles, we need to 180 - interior to get the exterior angle. since they're adjacent angles on a straight line.
so therefore we get
51 + 66 + x + 180 - 132 + 78 + 180 - 139 = 360 (sum of exterior angle of polygon)
284 + x = 360
x = 76°
so it's C.