formula for polyhedrons is V-E+F=2
F= faces = unknown F
V= vertices=F-8
E= edges=30
(F-8)-30+F=2
add the 2 F's and 30 & 8 so you get 2F-38=2
ince -38 doesn't have variable move it to other side by adding 38 to both sides
2F=38+2 which becomes 2F=40
now divide both sides by 2 to get F=20 so there are 20 faces
