How do i find the value of x so the slope of a line through (x,5) and (4,2) is 1/3?

The fence begins and ends with a post: {post = 0.5 feet}{chains = 5 feet}{post = 0.5 feet}...{chains = 5 feet}{post = 0.5 feet}

The minimum length is with 2 posts = 0.5 + 5 + 0.5 = 6 feet. To increase the fence, each time we should add{post = 0.5 feet}{chains = 5 feet}, so 5.5 feet. Thus, the lengths could be:

6 feet;

6 + 5.5 = 11.5 feet;

11.5 + 5.5 = 17 feet;

17 + 5.5 = 22.5 feet;

22.5 + 5.5 = 28 feet;

28 + 5.5 = 33.5 feet;

33.5 + 5.5 = 39 feet.

...

We skipped 35 feet.