24since u r in 9th class,,i dont think u need to start solving problems at this stage.....just conc on ur school syllabus and if u find time then start reading just theory of all the three subjects so as to generate ur intrest in the topics....
i would prefer university physics for physics and hall and knight for math ...just read hte theory and try to innovate things..u have a lot of time with u ..so dont worry...[1][1]