Table: tetrahedron
Columns: name
vertices_v
edges_e
faces_f
euler_characteristic_v_e_f

Question: What is the total number of E edges of the polyhedra with vertices V greater than 20?
SQL: SELECT COUNT("edges_e") FROM tetrahedron WHERE "vertices_v" > 20

Question: What is the lowest Euler characteristic: V-E+F of a hexahedron or cube, which has less than 20 faces F, less than 30 edges E, and less than 8 vertices V?
SQL: SELECT MIN("euler_characteristic_v_e_f") FROM tetrahedron WHERE "faces_f" < 20 AND "edges_e" < 30 AND "name" = 'hexahedron or cube' AND "vertices_v" < 8