Question 697119
Let 'x' be the initial speed of the car.
Let 't1' be the initial time taken to cover 715 kms

Therefore, t1  = 715 / x  -------------eq.1

If the speed is increased by 10, let new time taken be t2.

t2  = 715/(x+10) = t1-2 = 715/x  - 2

or {{{x^2+10x-3575=0}}}
or {{{x = 55}}} km/hr