Suppose that a city operates two neighborhood schools, one in the rich neighborhood and one in the poor neighborhood. The schools are equal in size and currently have equal budgets. The city receives $10 million in federal grant money that can be used to supplement the budgets of the two schools, which are initially identical. For each school, the average score on a standardized achievement test depends on how many dollars are allocated to the school. Letting S denote the average test score and X denote additional spending in millions of dollars, the relationships between scores and additional spending for the two schools are as follows: = Spoor 40+ Xpoor, Srich = 45 + 3X rich.