Answer:
The walkway would be 50ft.
Explanation:
To find this, we need to use the Pythagorean Theorem. In order to do this find the dimensions of the two sides of the garden. We can tell that the height is 30ft, due to the fact that the parallel height on the other part of the garden is that height.
We can also tell that the length of the triangular garden is 40ft. That's because the length of the larger garden is 70ft, but 30 of those are not in the secondary garden. So we use the two measurements in the theorem and find the hypotenuse.
a^2 + b^2 = c^2
30^2 + 40^2 = c^2
900 + 1600 = c^2
2500 = c^2
50 = c