Since while the money spent on advertising increases while the items sold increases, we have a positive relation between both variables.
By looking at where 30 is on the graph, we can see it lines up with 60,the middle between $40 and $80 on the y axis and so we know this is the cost associated with this value.
Step-by-step explanation: One pump can fill a swimming pool in 8 hours and another pump can fill it in 10 hours. If both pumps are opened at the same time, how many hours will it take to fill the pool?
