Complete the series 36, 54, 74, 96, 120, _______

Let's find the difference between consecutive numbers:
* $54-36=18$
* $74-54=20$
* $96-74=22$
* $120-96=24$

The difference increases by $2$ each time. The next difference must be $26$.
Therefore, the next number is $120+26=146$.