A gardener planted a total of $120$ flower bulbs consisting of tulips, daffodils, and crocuses. The number of daffodil bulbs planted was $d$. The number of crocus bulbs was $18$ less than the number of daffodil bulbs. The number of tulip bulbs was three times the number of daffodil bulbs. Which equation must be true for the value of $d$?