Find the value of r so the line that passes through each pair of points has the given slope.
40. In 1991, the federal minimum wage rate was $4.25 per hour. In 1997, it was increased to $5.15. Find the annual rate of change in the federal minimum wage rate from 1991 to 1997.
41. (6,2), (9,r), m=-1
42. (4,-5), (3,r), m=8
43. (5,r), (2,-3), m=4/3
44. (-2,7), (r,3), m=4/3
45. (1/2, -1/4), (r,-5/4), m=4
46. (2/3, r), (1,1/2), m= 1/2
47. (4,r), (r,2), m=-5/3
48. (r, 5), (-2, r), m=-2/9