Question 372553
Since this is a distance problem, you would use the rt=d equation.
2(t)=d
10(3-t)=d
You are not given the distance between Sylvia's and Cathy's houses, but since it is a two-way trip, you know that both equations cover the same distance.
So you can write 2(t)=10(3-t)
Multiply out 2t=30-10t
Transposing you get 12t=30.
Dividing by 12 you get t=2.5
Sylvia walked for 2.5 hours (and rode for half an hour)