Answer : The speed of walker and biker is, 16.67 mile/hr and 25.005 mile/hr respectively.
Step-by-step explanation :
Let the walker’s speed be, 'x'
So, the biker’s speed will be, 1.5x
Given:
Time = 1.5 hours
Distance between walker and biker = 12.5 miles
As we know that,

The distance covered by walker =

The distance covered by biker =

Distance between walker and biker = 12.5 miles
So,





Thus, the walker’s speed = x = 16.67 mile/hr
The biker's speed = 1.5x = 1.5(16.67) mile/hr = 25.005 mile/hr