$8-8+20x-3\left( 2x-3 \right)=9+14x$
Distribute $-3$ through the parentheses$8-8+20x-6x+9=9+14x$
Since two opposites add up to $0$, remove them from the expression$20x-6x+9=9+14x$
Cancel equal terms on both sides of the equation$20x-6x=14x$
Collect like terms$14x=14x$
The statement is true for any value of $x$, because both sides are identical$x \in ℝ$