What x Value makes this equation true?

X-3 = 3x + 7

So what you want to do is move all the variables to one side and numbers to the other.

x-3 = 3x + 7

So first move all the variables to one side:

x - 3x - 3 = 7

Then the numbers.

x - 3x = 7 + 3

Simplify

-2x = 10

Then divide both sides by - 2.

-2x = 10

/-2 / - 2

x = - 5