Question

What is one-quarter of one-twelfth?

Answer 1

One quarter of one twelfth is one-forty eighth 

Answer 2

Is means equal in mathematics
of means multiplication
and if we are solving for x then we can translate your equation to:

$\sf{x=\frac{1}{4}\times\frac{1}{12}}$

Simplifying that more, we get:

$\sf{x=\frac{1}{48}}$

And your final answer is:

$\huge{\boxed{\bf{\frac{1}{48}~is~\frac{1}{4}~of~\frac{1}{12}}}}$