Maths功課

Let the distance between Place A to Place B be x km and the time when Sam arrived at place B be y hours
Then , the time when Sam arrived at place B 10minutes earlier than Fanny , so the time of Sam is (y+1/6) hours
x=15y---------1
x=10(y+1/6)---------2
Sub 1 into 2
15y=10(y+1/6)
90y=60y+10
30y=10
y=1/3-------3
Sub 3 into 1
x=15(1/3)=5
Therefore,the distance between Place A to Place B is 5km