Answer:
British philosopher George Berkeley believed in immaterialism, which rejects the existence of physical matter and considers that material objects are only ideas of those who perceive them. In the quotation, he believes that it is impossible to know whether there are things outside the mind. In that matter, he maintains that there exists the same evidence now for thinking that there are things outside the mind, and that same evidence would also exist if there were no things outside the mind.
Sure!
One reason may be that persons younger than 18 will not always make responsible decisions, so entrusting them with electing officials might not be prudent.
A person younger than 18 might not vote for themselves, to reflect their own beliefs, but they might be influenced or even pushed to vote for a representative or measure of their parents' choosing.
People younger than 18 generally are not educated enough about politics and policies to make smart choices when it comes to voting.
Hope this helps!