First open the brackets. While opening brackets, you've to be careful about signs. So when you open bracket of <em>(</em><em>1</em><em>5</em><em>-</em><em>x</em><em>)</em>, there's <em>negative</em> sign in front of it, so it makes the signs inside the brackets to change. Then you solve the it.
Sketch the graph of the two by substituting x as 1, 2, 3 and you will see that the two graphs look exactly the same but seem to be reflected through the mirror line of the x-axis