Answer: This is a type of Synthesis reaction.
Explanation:
- Synthesis reaction is a type of chemical reaction in which two or more substances combine to form a single substance.

- Decomposition reactions are a type of chemical reactions in which a substance breaks down into two or more substances.

- Combustion reaction is a type of chemical reaction in which a hydrocarbon reacts with oxygen gas to produce carbon dioxide and water.

For the given reaction:

Here, 2 substances are combining together to form a single substance. Hence, it is considered as a synthesis reaction.
3/30=9/v
3×3=9
30×3= 90
v=90
A=base times height
A=10 times 7
A=70 cm²