Onome do polígono em que uma quantidade de diagonais é igual ao triplo do número de lados é?

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9

Ithink i know it but i want to be sure so can you me out ?

In which quadrant does the point lie? write the coordinates of the point. a. quadrant ii; (–2, –4) b. quadrant iii; (2, 4) c. quadrant iii; (–2, –4) d. quadrant iv; (–4, –2)