+230 First lets denote x to be how much mph he runs and 2x to be how much mph he bikes. We construct the following equation:
20/2x+10/x=2.5
10/x+10/x=2.5
10/x=1.25
x=10/1.25
x=8miles per hour
So there for his biking speed will be 2x=2*8=16miles per hour and his running speed will be 8 miles per hour.
