Explanation

The US House of Representatives voted Wednesday to impeach President Donald Trump on a single article of incitement of insurrection, making him the first president in US history to be impeached twice.

The 232-197 vote now sends the matter to the Senate for a trial that is expected to begin after Biden is sworn in Jan. 20. In all, 10 Republicans broke with their president in supporting his removal from office.

Explanation

Finding the pattern:

6−4=2

9−6=3

13−9=4

The differences between consecutive numbers are +2, +3, +4.

Following this pattern, the next difference should be +5.

So, 

13+5=18.