Question

a car travels first 180 kilometre at 80 kilometre per hour and next 180 km at 70 kilometre per hour find its a great speed​

Answer 1

Distance is same in both the cases, thus obviously 80km/hr speed is higher than 70km/hr

I think you are asking about average speed, if yes then, here it is: 74.66 kmph (74 2/3 kmph)

$average \: speed = 2v1v2 \div v1 + v2$