Is it possible to have Volume(solution) < Volume(solvent before adding solute)?
Gosh, sure. According to various on-line info (of unknown quality) a 2% by wt. solution of NaOH in water has a density of 1.0207 at 20°C. This means 100 g of it has a volume of 97.97 ml. At 20°C water has a density of 0.9982 meaning that 98 grams of water has a volume of 98.18 ml.