Matter is defined as material of substance which has mass and occupy physical space. Matter is some thing which contains atoms.So, from the given options the examples of matter are:
Salt dissolved in water: salt is made up sodium and chloride where as water is made of hydrogen and oxygen
air in the lower levels of the Earth’s atmosphere: air mixture of gases and gases are made atoms of different elements.
leather made from cow hides: processed product from the animal skin which is also made of organic matter that is carbon , hydrogen , oxygen and nitrogen.
metal after if has been molded; they too are made up of atoms.
