Answer:
53.7kPa
Step-by-step explanation:
Given parameters: 
Total pressure of the mixture = 96.4kPa
partial pressure of hydrogen = 13.4kPa
partial pressure of oxygen = 29.3kPa
Unknown: 
partial pressure of methane = ? 
Solution: 
The total pressure of mixture is equal to the sum of their particles pressures;
 
 Partial pressure of methane = 96.4kPa - (13.4kPa + 29.3kPa)
 Partial pressure of methane = 53.7kPa