Three times the square of a number means [tex]3x^2[/tex]
Nine times a number is [tex]9x[/tex]
If these quantities must be equal, we have
[tex]3x^2=9x[/tex]
We can divide both sides by 3 to get
[tex]x^2=3x[/tex]
Since x is non-zero, we can divide both sides by x:
[tex]x=3[/tex]