The cost of the pots is 3 * $20 = $<<3*20=60>>60
The cost of 4 pans is $100 - $60 = $40
Since each pan is the same price, the cost of 1 pan is $40 / 4 = $<<40/4=10>>10
The cost of 2 pans is $10 + $10 = $<<10+10=20>>20
#### 20