you could use the formula y-y1=m(x-x1)(point slope form) where m is the slope, y1 is the first y point and x1 is the first x point.
For example if a line has slope 3 and passes through the points (5, 6), then the formula you would solve is y-6=3(x-5) to find the equation of the line in slope-intercept form and you should know what to do with everything else.
if beginning is t = 0min Amount of sugar = 0, this is due to the fact that at the moment of entering the tank the content is only water
, but if beginning is t= 1min then;