# If X is polynomial-time reducible to Y and X is polynomial-time reducible to Z then Y is polynomial-time reducible to Z?

If $$X$$ is polynomial-time reducible to $$Y$$ and $$X$$ is polynomial-time reducible to $$Z$$,
$$Y$$ is polynomial-time reducible to $$Z$$?

If $$X \leq_p Y$$ and $$X \leq_p Z$$ then $$Y \leq_p Z$$?

True, false or we don’t know? Why?