Re read the question again just in case, try and put £25.50
But I got 25.5 too
You round down so 2.3 goes to 2
Place a point at (0,-5) because that is the y-intercept (the -5 on the vertical line)
Since the slope is negative two which can be re-written as -2/1 (rise/run) you go down two and to the right once or up two and to the left once, it doesn't matter which. Another point can be placed at (1,-7) or (-3,-1), it still doesn't matter which.
Then you can draw a line connecting the two points.
I hope this helps :)
Let me know if you need further explanation