Where does Rear driver side brake line tie to booster?

The rear driver side brake line typically ties into the brake master cylinder, not directly to the booster. The brake booster is connected to the master cylinder to enhance braking force, but the brake lines themselves run from the master cylinder to the brake calipers or wheel cylinders. The specific routing can vary slightly depending on the vehicle make and model. For precise details, it's best to consult the vehicle's service manual or schematic.