Solution :-
Let the usual speed of bus be x km/hr.
Time = Distance / Speed = 300/x hrs
According to the question,
=> (300/x - 2) (x + 5) = 300
=> (300 - 2x)/x (x + 5) = 300
=> 300x + 1500 - 2x² - 10x = 300x
=> 2x² + 10x - 1500 = 0
=> 2(x² + 5x - 750) = 0
=> x² + 30x - 25x - 750 = 0
=> x(x + 30) - 25(x + 30) = 0
=> (x - 25) (x + 30) = 0
=> x = 25 or x = - 30
∴ x ≠ - 30 (Because speed can't be negative)
Hence,
The usual speed of bus = 25 km/hr
