How do I write a range of numbers in a variable?

How do I write a range of numbers in a variable?
I need to make a ranking system for different kill counts.
here is my script:

	if player.leaderstats.Kills.Value >= 10 <= 19 then
			lowertext.Text = "Noob"
			lowertext.TextColor3 = Color3.fromRGB(10, 214, 255)
			na.Color = ColorSequence.new(Color3.new(0.384314, 1, 0.898039))
			na1.Color = ColorSequence.new(Color3.new(0.384314, 1, 0.898039))
			na2.Color = ColorSequence.new(Color3.new(0.384314, 1, 0.898039))
			na3.Color = ColorSequence.new(Color3.new(0.384314, 1, 0.898039))
			na4.Color = ColorSequence.new(Color3.new(0.384314, 1, 0.898039))
			na5.Color = ColorSequence.new(Color3.new(0.384314, 1, 0.898039))
			print("Color select")
		end

how can I write otherwise >= 10 <= 19?
a number from 10 to 19

player.leaderstats.Kills.Value >= 10 and player.leaderstats.Kills.Value <= 19