Take a taxi 10km, and pay the fare 10+( 10-3) × 2 = 24 yuan;
(1) 24+~15-10 ~× 3 = 39 (yuan)
(2) If the taxi mileage is 13. 1 km, the fare payable is 24+-14-10-× 3 = 38 > 31.
insufficient money
3 1 yuan money can sit at most10+-31-24÷ 3 ≈12 km away.
He must walk at least13.1-12 =1.1km = 1 100 meters.