
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
The pricing standard for taxis in a certain city is as follows: 10 yuan for distances up to 4km (inclusive), 1.2 yuan/km for the part exceeding 4km but not exceeding 18km; and 1.8 yuan/km for the part exceeding 18km.  
(1) If the cost of waiting time is not considered, establish the relationship between the taxi fare $y$ and the travel distance $x$;  
(2) If a person paid a taxi fare of 30.4 yuan, how many kilometers did he travel?

Present the answer in LaTex format: \boxed{Your answer}
user