1) from (1,2) to (3,1.5) two hours pass and the volume is reduced by 0.5
so every hour it decreases by 0.25 liters which is the last option
2) over 5 hours it decreased by 2 liters -> -0.4 liters/hour
which is the first option
3) 48*3=150-6=144 miles
so the first option
4) for a proportional relationship x/y=k with some constant c this means the slope can't change like the first graph also the line has to pass through (0,0) (otherwise the proportions would change, because y has some more/less) which only the 2 second graph fulfills)
second option
5) same reasoning, only the third graph has a constant slope and passes (0/0)
