At

[jack]

What do these mean?

1. ..where the customer lives an unusual distance from a populated area.
2. ..where the customer lives at an unusual distance from a populated area.

[Tdol]

They're both fine IMO and mean the same.

[jack]

Are these correct? If not, why? What do these mean?

1. He probabaly can get it half price.
2. He probabaly can get it at half price.
3. He probabaly can get it at halve price. (How do you know if you need to add -ed or not? How can I test it myself to see if it is wrong or not?)