A couple's wedding reception had 180 people. The bride and groom had each invited 20 couples from their side of the family. The remaining guests were friends. How many friends attended the reception?
From the bride's side, 20 couples * 2 guests/couple = <<20*2=40>>40 guests attended
From the groom's side, 20 couples * 2 guests/couple = <<20*2=40>>40 guests attended
Therefore 180 guests - (40 guests + 40 guests) = <<180-(40+40)=100>>100 friends attended the reception
#### 100