Answer:
All coelomates are triploblastic.
However, not all triploblastic organisms are coelomates.
Triploblastic simply means an organism contains all three germ layers of tissue (endoderm, mesoderm, ectoderm).
A Coelomate contains a fluid filled cavity within the mesoderm tissue layer. Coelomates developed in triploblastic organisms, because in order for this fluid filled cavity to exist, the mesoderm layer must be present.