Hi there!
A - The two similar triangles are Triangle ABC and Triangle ADX. (I cannot see the furthermost right letter on the triangle, which is why I used x in place of that letter. Be sure to change it when you submit this question!)
B - The scale factor here is 160/120 or 4/3.
C - In order to find the measure of the dotted line, we need to use the scale factor. Here is the equation we'll use: 4/3 = 70/x. Now, cross multiply to get 2
210 = 4x. Lastly, divide. The measure of the dotted line is 52.5 ft.
Hope this helps!! :)
If there's anything else that I can help you with, please let me know!