Correct Answer: He traveled at a speed of 9 km/hr.

Explanation:

Let. the speed be x km/hr.Since distance is 108 km, time $\frac{108}{x}$ hrs

When speed is increased by 3 km/hr, speed is = (x + 3) km/hr

so, The required time = $\frac{108}{x+3}$ hrs

According t0 the question,$\frac{108}{x}$-$\frac{108}{x+3}$ = 3

=> $\frac{108(x+3)-108x}{x(x+3)} =3$

=> 324 = 3x$^{2}$+9x

=> -3x$^{2}$ -9x+324 = 0

=> -3(x$^{2}$+3x-108) = 0

=> x$^{2}$+12x-9x-108 = 0

=> (x-9)(x+12) = 0

=> So either, x -9 = 0 Or, r + 12 = 0

If, x-9 =0 then x=9

If x + l2 = 0 then x =- 12

so, The speed 9km [Since velocity cant not be negative]He traveled at a speed of 9 km/hr. (ans)