Hmm... on a two-pan lab balance...
mass of object on the left pan has to be the same as that on the other.
Mass (copper, left) = Mass (lead, right pan) , mass = density x volume
therefore, density (Cu) x vol (Cu) = density (Pb) x vol (Pb), here you may make an optional table, so that you may not mismatch density and volume for one single object.
vol (Cu) = density (Pb) x vol(Pb) / density (Cu) = 11.4 x 2.05 / 8.96 = ___ cubic cm