Explain enthalpy change in single step is equal to the sum of enthalpy of several steps

Hess`s Law states that the heat transferred, or change in enthalpy (H), in a reaction is the same regardless whether the reaction occurs in a single step or in several steps. The method of calculating the enthalpy of reaction developed by Hess is called Hess`s Law of Heat Summation. If a series of reactions are added together, the net change in the heat of the reaction is the sum of the enthalpy changes for each step.