I'm guessing you have to solve for x. To do that, we must isolate it. So, let's subtract 3 from both sides first:
[tex]6x=18[/tex]
And now divide by 6 since that's the opposite of multiplication (6 is being multiplied to x):
[tex]x = \frac{18}{6} =3 [/tex]
So, your answer is x = 3.