solve(x^2-9x+18=0)

(x^2-9x+18=0)   factor this

(x - 6) ( x - 3) = 0       set each factor to 0

x - 6 = 0   add 6 to both sides          x - 3 = 0   add 3 to both sides

x = 6                                              x = 3

And thse are the two solutions