At a concert the ratio of adults to young people under 17 years old was 3 to 2 if the total number in attendance was 1620 how many adults attended the concert

I just learned this in school yesterday! :D

 Adult = 3
Young = 2

Add them together which is 5.
Divide 5 by 1,620 which is 324.
So you multiply back 3 x 324, because 3 is the adults. And you wanna find out how much adults are attended the concert. When you multiply 3 x 324, you get 972. So 972 is the answer! If you wanna find how many young people attended the concert, just multiply 2 and 324 together.

So, the answer to you question is: 972 Adults attended the concert.

Hope this Help :D