From the given information, we know that there are 3 students in the math club, and there are twice as many students in the science club as in the math club which means there are 3×2=6 students in the science club. However, we cannot simply add 6 to 3 because there are students who are in both clubs. There are 3, in this case, based on the question. Therefore, we need to subtract 3 from 6+3 which will be 6.