After his father gave him 13 biscuits, Randy has 32 + 13 = <<32+13=45>>45 biscuits.
After his mother gave him 15 biscuits, Randy has 45 + 15 = <<45+15=60>>60 biscuits.
After his brother ate 20 of the biscuits. Randy has 60 – 20 = <<60-20=40>>40 biscuits.
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