First keep in mind these two angles are equal to each other resulting in the equation needed to solve the answer has a = in it!
2x+39=6x-9
First subtract 2x from both sides ( 2x-2x and 6x-2x)
39=4x-9
Now add 9 to both sides (-9+9 and 39+9)
48=4x
Now divide both sides by four (4x/4 and 48/4)
x=12
