Simplify the radical 75 first:
[tex]\sqrt{75}[/tex]
5[tex]\sqrt{3}[/tex]
Next simplify the radical 12:
[tex]\sqrt{12}[/tex]
2[tex]\sqrt{3}[/tex]
Now that both radicals have the same number under the radical you can subtract the number in front normally
[tex]5\sqrt{3} -2\sqrt{3}[/tex]
[tex]3\sqrt{3}[/tex]
Hope this helped!
