I'm guessing that you meant to type 4(x - 3). If that's the case, then you can solve this using the Distributive Property.
4(x - 3) Multiply the number on the outside of the parentheses by both of the numbers on the inside.
(4 · x) - (4 · 3)
(4x) - (12) Now, simplify by taking out the parentheses.
4x - 12