[tex]\begin{gathered} \#areacodes=x\cdot y\cdot z \\ \\ x\colon anynumber1through9 \\ x=9 \\ \\ y\colon anynumber1through9 \\ y=9 \\ \\ z\colon anynumber2through9 \\ z=8 \\ \\ \\ \#areacodes=x\cdot y\cdot z \\ \#areacodes=9\cdot9\cdot8 \\ \\ \#areacodes=648 \end{gathered}[/tex]
