Answer: 25 moles of water are produced.
Step-by-step explanation:
Combustion is a type of chemical reaction in which fuel is reacted with oxygen to form carbon dioxide and water.
Example:

According to stoichiometry:
1 mole of methane on combustion produces= 2 moles of water
12.5 moles of methane on combustion produces=
moles of water
Thus 25 moles of water are produced from the combustion of 12.5 moles of methane.