Anim\:has\:16\:pots\:of\:equal\:size. \:he\:used\:9\:bags\:of\:potting\:soil\:to\:fill\:12\:of\:the\:pots. \:at\:that\:rate,\:how\:many\:bags\:of\:potting\:soil\:does\:amin\:need\:to\:fill\:the\:remainning\:4\:pots