To find the scale factor for the dilation of the isosceles right triangle, you can use the ratio of the lengths of the hypotenuses.
The original hypotenuse is 18 yards, and the new hypotenuse after dilation is 12 yards. The scale factor \( k \) is given by:
\[ k = \frac{\text{New Hypotenuse}}{\text{Original Hypotenuse}} = \frac{12}{18} \]
Now, simplify \( \frac{12}{18} \):
\[ k = \frac{2}{3} \]
Therefore, the scale factor you should use to dilate the triangle is \( \frac{2}{3} \).
So the correct response is:
Start Fraction 2 over 3 End Fraction