A Halide is a salt molecule, where a Halogen (F, Cl, Br, I, At) is present in the molecule with one other, less electronegative element

ie KCl, HAt, FeCl2

Sale 1

http://www.tf2outpost.com/trade/26809082 Sold for 21 keys

X = 21

Keys https://gyazo.com/1a99d72cea7595a962a350051002ac19 http://backpack.tf/profiles/76561198065215209?time=1444028400&compare=1444546800

Tossle http://backpack.tf/item/1346831210

Sale 2

http://www.tf2outpost.com/trade/27136679 Sold for 15 keys + KS Gold BK Sniper

B/O for Tossle was 20

X = 15 + 3.2*0.9

X = 18

Stuff http://backpack.tf/profiles/76561198056531196?time=1444374000&compare=1444460400

Tossle http://www.tf2outpost.com/item/440,4129472101,150,5

Sale 3

[No OP Trade] Sold for Gifted KS SF Scatter + 5 keys

X = 5 + 19*0.9

X = 22

Tossle http://backpack.tf/item/728239101

Scatter http://backpack.tf/item/609949878

Trade http://backpack.tf/profiles/76561198034095893?time=1446451200&compare=1446361200

Mini for Scatter

http://steamcommunity.com/market/listings/440/Strange%20Killstreak%20Festive%20Scattergun Sold for $53.70 on Nov 4th

53.7 + 53.7/1.15 = 100.40

100.40/2 = 50.20

Keys were $2.40 at time of sale

50.20/2.40 = 21 keys

Would be using but...

http://backpack.tf/stats/Strange/Killstreak%20Festive%20Scattergun/Tradable/Craftable Parted seller for 19, using 19