The % concentration in term of w/v or weight by volume can be determined by dividing the amount of solute by volume of solvent and taking its percentage. In this case, the solute is calcium hydroxide or Ca(OH)2 and has a weight (or mass) of 11 gm. The volume of the solvent is given as 173 ml.
Therefore, the concentration = mass of solute / volume of solvent x 100 %
= 11 gm/ 173 ml x 100% = 6.36% (w/v)
Thus, the given solution has a concentration of 6.36% (w/v).
We can similarly calculate the w/w concentration of the solution, by assuming the density of solvent (typically water) as 1 gm/ml.
% concentration (w/w) = mass of solute / mass of solvent x 100
= 11 gm / 173 gm x 100 = 6.36% (w/w)
Hope this helps.