Teddy has 7+8 = <<7+8=15>>15 pets in total.
Ben has 9+7 = <<9+7=16>>16 dogs, which means he has 16 pets in total.
Dave has 13+8 = <<13+8=21>>21 cats.
Dave has 7-5 = <<7-5=2>>2 dogs.
Dave has 21+2 = <<21+2=23>>23 pets in total.
Combined, they have 15+16+23 = <<15+16+23=54>>54 pets in total.
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