Since there are four clowns at the carousel this year, the candy seller sold 20*4 = <<20*4=80>>80 candies to all the clowns.
The thirty children also bought 20*30 = <<20*30=600>>600 candies in total.
Altogether, the candy seller sold 600+80 = <<600+80=680>>680 candies to the clowns and children at the carousel.
The number of candies the candy seller has left is 700-680= <<700-680=20>>20
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