Don't be lazy, it makes this site look bad.

Sale 1 QUICKSELL

http://www.tf2outpost.com/trade/25517514 Sold for 9 keys http://i.imgur.com/ByK9knq.png

X = 9

Topper http://backpack.tf/item/2655275177

Some of the Keys possibly used to buy this http://backpack.tf/item/2287908843

Sale 2

http://www.tf2outpost.com/trade/25155964 Sold for a bud on 27th Feb

B/O for Topper was 2

X = 11 keys

Bud http://backpack.tf/item/272321300

Topper http://backpack.tf/item/2655275177

Sale 3 QUICKSELL

[No OP Trade] Sold with a bud for Aces VRH + half a key of junk

Quite clear Trencher's was offered

X + 8 = 15 + 0.5

X = 15 - 7.5

X = 7.5 keys

VRH http://backpack.tf/item/2206382064

Bud http://backpack.tf/item/143703080

Topper's http://backpack.tf/item/2655275177

Mini for VRH

Plenty of sellers for 15 keys on classifieds, using 15

Sale 4

http://www.tf2outpost.com/trade/25071345 Sold for Lantern Sack

B/O for Trencher's was 17 keys

Sack had no trade, presuming offered

Took less than a day making Sale 1 invalid

X = 1.2*0.9

X = 1.1

X = 13 keys at time of sale

Sack http://backpack.tf/item/547592940

Topper http://backpack.tf/item/2655275177

Sack wasn't outdated at the time (1.2)