rate * time = distance
distance/rate = time
105 minutes moving time Bike time = distance/rate = 20/(2x+1)
Run time = 5/x
added together the time = 105 min = 1.75 hr
20/(2x+1) + 5/x = 1.75
20x /(2x+1) + 5 = 1.75 x
20 x + 5(2x+1) = 1.75 x (2x+1)
20 x + 10x + 5 = 3.5 x2 + 1.75x
3.5 x^2 -28.25x -5 =0
x = 8.24 m/hr running speed (via quadratic formula)