From the children, there are a total of 11 children * 4 items of clothing each = <<11*4=44>>44 items of clothing on the clotheslines.
From the adults, there are a total of 20 adults * 3 items of clothing each = <<20*3=60>>60 items of clothing on the clotheslines.
So there are a total of 44 + 60 = <<44+60=104>>104 items of clothing on the clotheslines.
This means that there are 104 items of clothing / 2 items of clothing per clothesline = <<104/2=52>>52 clotheslines.
There are 2 clotheslines per house so there must be 52 clotheslines / 2 = <<52/2=26>>26 houses on the street.
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