Answer:
Paul should be wearing a light jacket appropriate for about 59 F or 15 °C
Explanation:
If it is 4:00 a.m. in Honolulu when it is 2:00 p.m. in London, then the difference between times is:

London is 10 hours ahead of Honolulu.
If Paul left Honolulu at 12:00 p.m, the corresponding time in London was:

Since he arrived in London at 1:00 p.m. at Friday, the flight time was:

The flight took 15 hours in total. If the temperature was 30°C when he boarded the flight and it decreases at a rate of 1°C per hour, the temperature when Paul arrives in London is:

Converting it to Fahrenheit

Paul should be wearing a light jacket appropriate for about 59 F or 15 °C