I found it very useful that I did not have to write or read, and if a problem came up I just called the qualified teacher.

came 是动词 come 的过去式，表示"来、到达"。 up 是副词，表示"向上、出现"的意思。 came up 是一个短语动词，意思是"出现、发生"，通常指问题或情况的突然出现。