Tend to Your Business

 is a quest in Fallout: New Vegas.

After replacing the Brotherhood Elder with Head Paladin Hardin, he will ask you to go to Freeside and kill all the Van Graffs and their men to prove your loyalty.

Quick Walkthrough
The easiest way to complete this is to set C-4 Explosives down at the feet of each person in the Silver Rush. Since they aren't hostile to you, they will stay in place despite this. Then simply head to the bathroom, well outside the blast radius, and set the C-4 off with the Detonator.

An even easier way is to ask the weapons saleswoman if she has any work for you. She will assign you work as a door guard. The third or so 'Gambler' to approach the door will say that he wants to replace his Revolver. Let him in, saying that, since he declared his weapon, he's good to go. Enjoy the result.

You can kill them all during the botched arms deal to the Legion, then go back kill the doorman and you win.

You may also try killing them with the Anti-Material Incendiary ammo glitch.(needs confirmation)

With a sniper rifle modded with the suppressor equipped, find an area where you are 'hidden' while sneaking, and hit the guards in the head for a one shot kill, that leaves the others unaware. Attacking any named character in this manner will cause all factions members to be hostile toward you, so make sure to kill the guards before you target Van Graffs or Simon.

There is a "dead spot" behind the pool tables where you can sit and hide. So with the Incinerator burn them up and run behind the table. Enemies can shoot but will hit table and you can still burn them with Incinerator.

(This Quest is the alternative to Eyesight to the Blind, which is Elder McNamara's loyalty quest. You can only do the quest specific to the Elder you chose to support, which is decided once Still in the Dark is completed.)