8.5x+51.86=-11.5x+51.76

Add, - 11.5x and move it over to 8.5x

Then, subtract them together and you get 20x + 51.86 = 51.76

And you move (subtract) 51. 86 over to 51.76, subtract that and you get 20x = - 0.1

Divide, and your answer is - 200