You can find the area of Bonnue's backyard by comparing the hypotenuse of the garden to the hypotenuse of the back yard. If the hypotenuse of the garden is 10 (with the side lengths being 6, 8 and 10 - the longest is always the hypotenuse) and the hypotenuse of the back yard is 30, this is a scale factor of 3 (3 times longer).
This means the other two sides would also be 3 times longer.
6 yards x 3 = 18 8 yards x 3 = 24
To find the area using these dimensions, you will use the formula for finding the area of a triangle.