1. The problem asks to write an equation in the form $y = mx + b$ for the given graph. 2. The graph shows a line passing through the origin $(0,0)$ and points increasing by 20 units in $y$ for every 1 unit increase in $x$. 3. The slope $m$ is calculated as the change in $y$ over the change in $x$: $$m = \frac{20 - 0}{1 - 0} = 20$$ 4. Since the line passes through the origin, the y-intercept $b = 0$. 5. Therefore, the equation of the line is $$y = 20x + 0$$ This means for every minute, the water increases by 20 gallons starting from 0 gallons at time 0.