Answer:
(1) To find the number of students who have taken French, we need to subtract the number of students who have taken English but not French from the total number of students in the class. So, the number of students who have taken French would be 30 - 10 = 20.
(2) To find the number of students who have taken French but not English, we need to subtract the number of students who have taken both French and English from the total number of students who have taken French. So, the number of students who have taken French but not English would be 20 - 15 = 5.