In a junior high school, 30% of the students in the Math Club are in the Science Club and 80% of the students in the Science Club are in the Math Club. There are 15 students in the Science Club.
The number of students in the Math Club is
15x80/100=15x4/5=12
30%=12
10%=4
100%=$\boxed{40}$
+409 
