N2 and H2 are mixed in 14:3 mass ratio. After xertain time ammonia was found to be 40% by mole. The mole fraction of N2, H2 and NH3 is:

Base change rule means if you have some log a to the base b, then you can write it as (log a to the base c/log b to the base c), where both a and b have same bases c.
For example,
Log2 to the base10 can be written as:
log2 to the base 2/log10 to the base 2,
Where the base 2 belongs to both 2 and 10.