The running speed is 2 mi/hr
Using the formula for calculating his speed;
Speed = distance/time
Let his running speed be "s"
If his biking speed is 12 mph faster than his running speed, then biking speed is s + 12
If he ran 9 miles and biked for 135 miles, then the required speed will be expressed as:
s + 12+s = 135/9 + 9/9
2s + 12 = 144/9
2s + 12 = 16
2s = 16 - 12
2s = 4
s = 4/2
s = 2
Hence the running speed is 2 mi/hr
Learn more on distance here: https://brainly.com/question/13664094
