Answer:
B. y = 2.5
Step-by-step explanation:
Diane's average speed= 25/y km/h.
Ed's speed= (25/y) - 6 km/h.
Ed walks 25-3 = 22 km.
Consider Ed's journey:
Speed = distance / time so:
(25/y) - 6 = 22 / (y + 3) ( 3 hours longer = y + 3)
(25 /y - 6)(y + 3) = 22
25 + 75/y - 6y - 18 = 22
6y - 75/y = 25 - 18 - 22
6y - 75/y + 15 = 0
6y^2 + 15y - 75 = 0
2y^2 + 5y - 25 = 0
(2y - 5 )(y + 5) = 0
y = 2.5, -5.
y = 2.5 ( as it must be positive.
