What is the length of a ketchup

(note i put the graph in so plz )the graph shows the amount of water that remains in a barrel after it begins to leak. the variable x represents the number of days that have passed since the barrel was filled, and y represents the number of gallons of water that remain in the barrel. what is the slope of the line

Find the constant of variation for the relation and use it to write an equation for the statement. then solve the equation.

Someone answer this check out the image!