Calculate the compositions of the systems indicated below using the right triangle diagram and analytical methods. a) From 500 kg of a mixture of composition by weight: 20% water, 30% salt and 50% sand, and 80 kg of water are evaporated.

b) 100 kg of a mixture of composition by weight: 50% salt, 10% water and 40% sand; 100 kg of another containing 20% salt, 70% water and 10% sand are added. 50 kg of water are separated by evaporation and 15 kg of salt are added.

c) From 500 kg of a mixture of 50% salt, 20% sand and 30% water, 300 kg of a mixture of 60% salt, 25% sand and 15% water are separated.