Combination (also called synthesis): Where two elements or one compound and one element will bond and form a new compound as a product, the representation for this reaction is:
A + B -> AB
Decomposition: The opposite from Combination, now one compound will decompose and form 2 new elements or compounds as the product:
AB -> A + B
Single Replacement: One element will take the place of another element in already existing compound:
A + BC -> AB + C
Double Replacement: Now we have two compounds switching elements and forming two new compounds:
AB + CD -> AC + BD
Combustion: Reactions that involve oxygen as reactant and we have CO2 and H2O as products:
X + O2 -> CO2 + H2O
For our question, we have a Decomposition reaction