7 books • 4 series
Cambridge IGCSE® Mathematics Extended Problem-solving Book (Cambridge International IGCSE)
GCSE Mathematics for Edexcel Foundation Problem-solving Book (GCSE Mathematics Edexcel)
GCSE Mathematics for Edexcel Higher Problem-solving Book (GCSE Mathematics Edexcel)
GCSE Mathematics for AQA Foundation Problem-solving Book (GCSE Mathematics AQA)
GCSE Mathematics for AQA Higher Problem-solving Book (GCSE Mathematics AQA)
GCSE Mathematics for OCR Foundation Problem-solving Book (GCSE Mathematics OCR)
GCSE Mathematics for OCR Higher Problem-solving Book (GCSE Mathematics OCR)