Euler's formula for a polyhedron is given by:
[tex]\begin{gathered} F+V=E+2 \\ \text{where,} \\ F=\text{faces} \\ V=\text{vertices} \\ E=\text{edges} \end{gathered}[/tex]
Make E, the subject of the formula:
[tex]\begin{gathered} F+V=E+2 \\ E=F+V-2 \end{gathered}[/tex]
Put F = 20, V = 12, to obtain E,
[tex]\begin{gathered} E=20+12-2 \\ E=30 \end{gathered}[/tex]
Therefore, there are 30 edges
