Answer:
4 miles
Step-by-step explanation:
Let
x ----> the time to returned back biking in hours
d ---> the distance in miles
s ---> speed in miles per hour
Remember that
The speed or rate is equal to divide the distance by the time
[tex]s=\frac{d}{t}[/tex]
The distance is equal to multiply the speed by the time
[tex]d=st[/tex]
we know that
[tex]18\ min=\frac{18}{60}\ hours[/tex]
The distance to his friend's house and the distance of return is the same
so
[tex]10x=4(x+\frac{18}{60})[/tex]
solve for x
[tex]10x=4x+\frac{18}{15}[/tex]
subtract 4x both sides
[tex]10x-4x=\frac{18}{15}[/tex]
[tex]6x=\frac{18}{15}[/tex]
[tex]x=\frac{1}{5}\ hours[/tex]
The total distance of the round trip is
[tex]y=10x+4x+\frac{18}{15}[/tex]
substitute the value of x
[tex]y=10(\frac{1}{5})+4(\frac{1}{5})+\frac{18}{15}[/tex]
[tex]y=2+2=4\ miles[/tex]
