script to teleport one random player?

I need a script to teleport one random player in coordinates -687.5,34.7,52.5

This is simple. You teleport players via:

player.Character:SetPrimaryPartCFrame(CFrame.new(-687.5,34.7,52.5))

The more complicated part is randomizing the players.

That would need a more complex script:

local function teleportRandom()
	local players = game.Players:GetChildren() --All the players
	local num = 0 --Number of counted players
	local count = 0 --Current player being served
	
	for _, player in ipairs(players) do --Counts all the players
		num = num + 1
	end
	
	local rand = math.random (1, num) --Selects one random player
	
	for _, item in ipairs(players) do --Tries to find selected player
		count = count + 1
		if rand == count then --Checks if player is the one
				item:LoadCharacter() --Respawns the player
				item.Character:SetPrimaryPartCFrame(CFrame.new(-687.5,34.7,52.5)) --Teleports player
		end
	end
end