Answer:
11 km/h
Step-by-step explanation:
What I did is found out how fast the simulated biker traveled for 15 minutes, by doing
[tex]\frac{20}{4}[/tex] = 5
Since 15 minutes is 1/4 of an hour. Or you could do 20/60 = 1/3,  1/3 being  how much the biker traveled in a minute and multiply that by 15
15×[tex]\frac{1}{3}[/tex] = 5
Now we know that the biker traveled 5 km, now subtract 5 by [tex]2 \frac {1}{4}[/tex]
5 - [tex]2 \frac {1}{4}[/tex] =   [tex]2 \frac {3}{4}[/tex]
Julian traveled  [tex]2 \frac {3}{4}[/tex] in 15 minutes, now to find his average speed you multiply [tex]2 \frac {3}{4}[/tex] by 4 since [tex]2 \frac {3}{4}[/tex] is the distance traveled in 1/4 an hour.
[tex]2 \frac {3}{4}[/tex] × 4 = 11
11 km/h
