Simplify
\[
\sqrt{36x^{2} - 108x + 81}
\]
What will be the value of
\[
\frac{\tan 45^\circ - \tan 15^\circ}{1 + \tan 45^\circ \, \tan 15^\circ}
\]
Select the most appropriate meaning of the underlined idiom in the given sentence.
A fair-weather friend can never be trusted in the times of exigency.
A close friend
A pen friend
A selfish friend
An old acquaintance
Select the most appropriate option that can substitute the underlined segment in the given sentence.
Unemployment has become a fiery question of the day.
become a burning question
become a freezing question
become a furious question
become a flaming question