Answer: 21.6 feet
Explanation:
Hi, to answer this question we have to apply the Pythagorean Theorem:
The rectangular yard can be seen as two right triangles divided by a diagonal (see attachment)
c2 = a2+b3
Where C is the hypotenuse of a right triangle (in this case, the diagonal of the rectangle) and a and b are the other sides.
Replacing with the values given:
c^2 = 12^2 + 18^2
c^2= 144+324
c^2 = 468
c = √468
c = 21.6 feet
Feel free to ask for more if needed or if you did not understand something.