If the question includes x only than it’s value would be 1
11. D
12.C
13. For 13 i would say B but not so sure
14. A
Answer:
opción c es la respuesta correcta espero que te ayude
Answer:

Explanation:
Hello there!
In this case, for the reaction by which water is decomposed to molecular hydrogen and oxygen:

It is necessary to perform the inspection balance process since there is a dissimilar number of atoms of oxygen on both sides; therefore, by putting a 2 on water we balance oxygen:

But now, there are four hydrogens on the left; therefore, we put a 2 on hydrogen to finally balance it:

And obviously, the coefficient in oxygen is an unwritten 1.
Best regards!