The two t-shirts amount to $8 x 2 = $<<8*2=16>>16.
The two bags amount to $10 x 2= $<<10*2=20>>20.
So Timothy spent $16 + $20 = $<<16+20=36>>36 for the shirts and bags.
He still has $50 - $36 = $<<50-36=14>>14 left to spend for the key chains.
With the money, he can buy $14/$2 = <<14/2=7>>7 sets of key chains.
Therefore, he can buy 7 x 3 = <<7*3=21>>21 pieces of key chains.
#### 21