in normal water means soft water we add salt then it will became hard water and it will not possible for us to clean clothes in it ..? give reason

Soft water is water which contains little or no salts of calcium and magnesium. If water contains less than 85.5 parts per million of calcium, it is soft water. Hard water is water which contains minerals. It contains specially bicarbonates, chlorides and sulphates of calcium and magnesium. It is called hard water because it leaves behind deposits which damage plumbing,coolers and so on. 

Hard water does not form lather as it contains calcium and magnesium ions which react with soap. As soap is sodium or potassium salt of higher fatty acids, calcium and magnesium ions present in water react with anions of fatty acid to form a white precipitate or insoluble scum, which sticks on clothes and instead of cleaning the clothes make them dirtier. In this way a large amount of soap is also wasted and hence washing clothes with hard water makes the washing or cleaning difficult.

Regards.