



 
Hi Nicky, I would prepare a table with two columns, one for the number of sides of the polygon and the other with the number of diagonals
and look for two rows where the sum of the number of sides is 12 and the sum of the number of diagonals is 19. How do you know the number of diagonals in each row? I can suggest two ways. Draw a diagram and count the number of diagonals or use an algebraic expression for the number of diagonals. Better yet, do both. Penny  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 