Hi,
1. 25 hours worth of work is not a massive heap, so you should be fine in 3 weeks.
2. Put in some solid time and effort to master the subject material.
3. Try and associate/interlink facts from different parts of the syllabus to aid memory.
4. Make notes - memory functions multimodally i.e. uses all your senses, so the act of moving your hand/fingers to write will enhance memory retention and recall.
5. Use my tried and tested exam tips: chk out attachment.
BEST OF LUCK! 6. BE POSITIVE - the best achievers in exams are optimists!