Explanation:
sqrt(48) = 6.9282032302755091741... =
= 6.928...
I am not sure how your teacher wants you to do this.
the above form is the most common form to represent this (we see there is no repeating pattern, so it is irrational).
for a rational number we would show the repeating pattern underlined before going on infinitely ("...").
like
1/30 = 0.033333333... = 0.03...
there is also the possibility to add a P at the end (as the symbol for irrational numbers as the difference of the sets of R and Q : real numbers - rational numbers) :
6.929P