The simplification required is to remove the root from the denominator of the fraction (so that roots are confined to the numerator).
This may be achieved by multiplying by #1# (so that the value of the overall expression is unchanged), but choosing an appropriately constructed expression that evaluates to #1# (noting that anything divided by itself (excluding zero) equals #1#).
The specially chosen instance of #1# requires a number in its denominator that will remove the root. This can be achieved by multiplying by something divided by #sqrt(3)#, as #sqrt(3) xx sqrt(3) = 3#. To ensure the complete number is #1#, the numerator must also have #sqrt(3)#.
So, the required simplification is
#(11y)/sqrt(3) xx sqrt(3)/sqrt(3)#
#(11ysqrt(3))/3#