Sale 1

http://backpack.tf/profiles/76561198002186909#!/compare/1464652800/1464739200

http://backpack.tf/profiles/76561198207982677?time=1464739200 (sort by time)

http://imgur.com/a/75Hmn

Sold for 15 keys

X = 15

Sale 2

http://backpack.tf/profiles/76561198061376237#!/compare/1459468800/1459555200

http://backpack.tf/profiles/76561198061376237?time=1459555200 (sort by time)

http://imgur.com/a/nrkPh

Sold for C9 Topi + 7 keys of sweets

X = 13.5 + 7

X = 21

Sale 3

http://backpack.tf/profiles/76561198147356475#!/compare/1461801600/1461888000

Sold for C9 Escorter + 4 keys

X = 14 + 4

X = 18

Sale 4

http://backpack.tf/profiles/76561198156429176#!/compare/1462579200/1462665600

Sold with Thunderbolt Sniper for OP Tree

X + 3 = 19

X = 16

Sale 5

http://backpack.tf/profiles/76561198168316519#!/compare/1462838400/1462924800

Sold with 6 keys for Electric Hot Air

X + 6 = 21

X = 15

Sale 6

http://backpack.tf/profiles/76561198168316519#!/compare/1462924800/1463011200

Sold with 6.5 keys of sweets for Phosphorous Billycock

X + 6.5 = 27

X = 21