1. The problem statement, all variables and given/known data The densities (at 25*C) of tin and lead are 7.3 g/cm3 and 11.3 g/cm3 respectively. Plumber's solder is an alloy of tin and lead and has a density of 9.7 g/cm3. Estimate the composition by mass, of the two metals in this solder. 2. Relevant equations 3. The attempt at a solution i assumed the % composition of lead to be X%. so % composition of tin is (100 - X)%. using [(X*11.3)/100] + [((100-X)*7.3)/100] = 9.7 i got % lead as 60% and % tin as 40%. but the answers from the book are 30.1% for tin and 69.9% for lead. any help!