Blanche found 3 pieces of red and Rose found 9 pieces of red for a total of 3+9 = <<3+9=12>>12 pieces of red
Dorothy found twice the amount of red as her friends so she has 2*12 = <<2*12=24>>24 pieces of red sea glass
Rose found 11 pieces of blue sea glass and Dorothy found 3 times that amount so she had 11*3 = <<11*3=33>>33 pieces of blue glass
Together, Dorothy found 24 red and 33 blue so she had 24+33 = <<24+33=57>>57 pieces of sea glass.
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