Brake line to back wheel cylinder

Typically a 10mm line wrench will help you remove the line. This video show the job being done on a similar car.

https://youtu.be/1j7qDoi1LP0

Be sure to use a flare nut wrench if you want to save the line. Open end wrenches can be expected to round off those soft brass nuts. If you're replacing the line, cut it off at the nut and use a six point deep socket. If you're replacing the wheel cylinder and the nut is rusted to the line, it's going to twist the line off. Just loosen it instead, then unbolt the wheel cylinder and spin it off the nut.

Please let us know if you need anything else to get the problem fixed.

Cheers