In the formal language of economics, X and Y are substitutes if the demand for X increases when the price of Y increases, or a positive cross elasticity of demand.
Potting mix is the material that goes into a garden pot before you put seeds and plants into it. 1  It keeps the plant in place. 2  It holds water for the plantâs roots to soak up.  It contains nutrients that feed the plant.
What Is Dry Mix Concrete. To understand what dry mix concrete actually is, you need to know what it is made of. Concrete is a mixture of cement, different types of aggregate material, and water that when mixed together will harden into any shape that you want. This is commonly what is used on sidewalks, driveways, and is also used in the creation of precast materials for the structure of large buildings that you see today.