Question

please give me answer​

Answer 1

$original \: speed = x \: kmph \\ time \: taken \: to \: travel \: 1200km = \frac{1200}{x} hours \\ new \: speed = x + 5 \: kmph \\ new \: time \: taken = \frac{1200}{x + 5} hours \\ difference \: between \: times = 8hours \\ \frac{1200}{x} - \frac{1200}{x + 5} = 8 \\ \frac{1}{x} - \frac{1}{x + 5 } = \frac{1}{150} \\ \frac{5}{ {x}^{2} + 5x } = \frac{1}{150 } \\ {x}^{2} + 5x = 750 \\ {x}^{2} + 5x - 750 = 0 \\ {x }^{2} + 30x - 25x - 750 = 0 \\ x(x + 30) - 25(x + 30) = 0 \\ (x + 30)(x - 25) = 0 \\ x = 25kmph$

$hence \: original \: speed \: is \: 25kmph$