Of the under-30s there for the second band, 40% are men because 100-60 = <<100-60=40>>40
There are fifty under-30s there for the second band because 20 / .4 = <<20/.4=50>>50
There are 100 people there to see the second band because 50 / .5 = <<50/.5=100>>100
There are 150 people at the concert because 100 / (2/3) = <<100/(2/3)=150>>150
#### 150