Think of 2 points: (60, 52) and (125, 65).
65-52 13 1
The slope of the line thru these pts is m = ----------- = ----------- = ---
125-60 65 5
Then the equation of the line is found from y = mx + b, which here is
125=(1/5)(65) + b
Then 125 - 13 = b, or 112 = b
The equation of this line is then y = 5(x) + 112.
Notice that when x =, the jar is empty. It weighs 112 oz.