Yea so whats the question or is that just a fact<span />
Let's examine this, as x increases by 1, what happens to the y-value? The y-value decreases by 2, so the slope is -2. When x = 0, we have our y-intercept, -5. So we can fill in Slope form with the Slope and Y-intercept that the equation is:
y = -2x - 5
We need to find a common denominator(bottom number of fraction)
5/3 = 25/15 (multiply both top and bottom by 5)
1/5 = 3/15 (multiply both top and bottom by 3)
Now since the denominator is the same we can add to get 25/15 + 3/15 = 28/15