Agroup of 16 friends visited an amusement park. when they arrived, 3/4 of the friends wanted to ride the fastest roller coaster first. how many friends wanted to ride?

First, divide 16 into fourths.

16/4 (or, how many times does 4 go into 16?) equals 4.

Now, because you need three fourths, simply multiply that number by 3. 
4 x 3 = 12

So your answer is 12 friends.

Hope this helps!