Answer: -21
Step-by-step explanation:
To begin, we can combine like terms, -0.66 and 0.36 are coefficients with the same variable.
This gives us -0.66x+0.36x= -0.30x, and the equation becomes -0.30x=6.3.
Next, we can simply solve for x by dividing 6.3 by -0.30, and that gives us x=-21.