Let the distance to the market be .
The distance travelled in the first 5 minutes is:
35 m/min * 5 min = 175 m.
So after having travelled these 175 meters, the distance left is .
First of all, if he continued to walk at an average speed of 35 m/min, then the time spent would be
But since he increases his speed by 10 m/min on the last distance of x-175 m, the actual time is
You are being told that this actual time is 2 minutes less than the time
so you just need to solve the equation
I get , but check that I'm right.