Harry drove for 3 hours on the​ freeway, then decreased his speed by 20 miles per hour and drove for 6 more hours on a country road. If his total trip was 483 ​miles, then what was his speed on the​ freeway?

Respuesta :

х (miles per hour)  -  his speed

3x + (x - 20) * 6 = 483
3x + 6x - 120 = 483
9x - 120 = 483
9x = 483 + 120 
9x = 603
x = 603 : 9
х = 67 miles per hour - his speed on the freeway - answer.