Find the missing numbers ($X$ and $Y$) in the series and find the value of $Y-X$:
10, 30, 20, X, 50, 150, Y

Let's examine the multi-operation pattern of the series step by step:
* $10\times 3=30$
* $30-10=20$
* $20\times 3=X⟹X=60$
* $60-10=50$
* $50\times 3=150$
* $150-10=Y⟹Y=140$

Now, we calculate the required value $Y-X$:

$$Y-X=140-60=80$$