How do you this? i need for this.

You have two types of terms here, two variables (terms with x attached to then) and a constant (a number by itself)
You just need to get the two different types of terms individually, on either side of the equal sign:
-4x=-2x+6
Add 2x on both sides to remove the variable from the right hand sign
-2x=6
Divide both sides by -2(the coefficient of x)
x= -3
x is on the LHS and -3 is on the RHS

The answer is 6 weeks