Can I get some help with this one?

There are  15  people in the science club.

80% of the people in the science club are in both the science and math clubs, so...

number of people in both clubs  =  0.8 * 15  =  12

Let the number of people in math club  =  m

30% of the people in the math club are in both the science and math clubs,

and remember there are  12  people that are in both clubs, so...

0.3m  =  12

m  =  12 / 0.3

m  =  40

There are 15 students in the Science Club.......80%  of these are in the Math Club....

Note that 80%  =  4/5....so 4/5 * 15  =  60/ 5 = 12 

So....12 students in the Science Club are Math Club members

And these 12 represent 30% of the Math Club

Call the total members in the Math Club, M

So.....

30% of M  = 12      or, put another way

.30 M  = 12        divide both sides by .30

M  =  12 / .30  =  40 students in the Math Club

Sorry, hectictar.....I didn't see that you were answering, too....  

Aha....a "stealth" answerer...........the sneakiest kind.....LOL!!!

They'll sneak up right behind you...and suddenly....BOO!!

It  is close to Halloween, after all !!! Gotta watch out!!