A car covers 25 km at a uniform speed. If the speed had been 8 knv/h more, it would have taken 10 hours less for the same journey. What is the speed of the car (in km/h)?

We know that :
Distance covered = speed * time
Now let speed be v km/hr and time taken initially be t hrs
Now we get vt=25     (1)
Also (v+8)(t-10) =25     (2)
Now equating (1) and (2)
we get vt =vt +8t-10v-80
we get 8t -10v =80
or 4t -5v =40    (3)
Now substituting $$t=\frac{25}{v};\ we\ get\ $$
$$\frac{100}{v}-5v\ =40$$
or $$100-5v^2\ =40v$$
or $$5v^2+40v-100\ =0$$
we 5(v+10)(v-2) =0
as v cannot be negative
so we get v= 2 km/hr