Question

Which law of chemical combination is illustrated by the fact that 168 g Fe reacts with 72 g H2O to from 232g Fe3 O4 and 8g H2

Answer 1

In this case 
168g + 72 g = 240 g LHS  Reactants 
232g + 8g = 240 g RHS Products
law of conservation of mass

Answer 2

ya the above one is correct by this chemical reaction law of conservation of mass illustrated