Question 202364
You're on the right track, but have an error in the logic used to represent the bus ride time
Let t be the time it takes to walk in hours. Then bus ride time is {{{t-15/60}}} (remember your time needs to be in the same units. So we have to convert 15 minutes into hours)
You know that {{{Distance=Rate * time}}}
And you also know the distance is the same in both directions.
So {{{BusDistance = WalkingDistance}}}
{{{BusRate*BusTime = WalkingRate*WalkingTime}}}
{{{60 * (t-(1/4)) = 10*t}}} <--- this is where your error in bustime messed you up
{{{60t - 15 = 10t}}}
{{{50t = 15}}}
{{{t = 0.3}}} hours
That's 18 minutes. 
If Bong walks at 10kph for 0.3 hours, thats {{{Distance = (10k/h)*0.3h}}} = {{{3k}}}