Complete the series: $18,40,70,108,\_\_\_\_\_\_\_$.

Let's track the sequence differences:
* $40-18=22$
* $70-40=30$
* $108-70=38$

The differences ($22,30,38$) increase steadily by $+8$ each time. Following this rule, the next difference is $38+8=46$.

$$\text{Next term}=108+46=154$$