Normally there are twenty... you can either recognize the icosahedron pattern, or count them. Each pentagon clearly has five hexagons adjacent, and each of those hexagons is adjacent to three pentagons. So you take 12 (#of pentagons) * 5 = 60, and divide by 3 (because you've counted them all three times), and get 20.
However, this ball has an error in the first panel... one of the pentagons has six polygons around it.
