In order to find an equation of the line shown in the graph, we'll use the two points given: (0,5) and (-1,0). First of all, let's find the slope of the line:

So, the slope is m=5.
The equation of the line will be:
y-y0 = m(x-x0)
y-0 = 5(x+1)
y = 5x+5