The equation ΔHsoln = ΔH1+ΔH2+ΔH3 means that either the solution is endothermic (ΔH < 0, the resulting reaction is cold) or exothermic (ΔH>0, the resulting reaction is hot). The lattice energy can be solve through this equation,
lattice energy = ΔHsolvation - IMF - ΔHsoln