using a circle graph with 1/3 percussion, 2/5 brass, 4/15 woodwind. There are 30 musicians in the band. How many of them play bass instruments?

I think I have to multiply 30 times 2/5 and in simplest form my answer would be 12. Is this correct?

Yes, you are correct. To find out how many musicians play bass instruments, you need to multiply the total number of musicians in the band (30) by the fraction representing the proportion of brass players (2/5):

30 * 2/5 = 12

Therefore, there are 12 musicians who play bass instruments in the band.