This math problem has got me stumped: Katerina makes designer jewelry.  Her specialty is topaz necklaces.  She uses 8 topaz gemstones per necklace, and fills the space between gemstones using sterling silver beads.  If each topaz gemstone is one inch long, each sterling silver bead is one-quarter of an inch long, and each necklace is made to a total length of 25 inches, how many sterling silver beads does Katerina use per necklace?
Can you show me the way?