My sister maths problem, how to do, thanks?

(a)
Distance = Speed × Time
Jenny walked 5x km to the south, took a break and walked 5y km to the north until 1 p.m.
Therefore, at 1 p.m. her position is (5x - 5y) km relative to her home.

(b)
From 9 a.m. to 1 p.m. there were 4 hours.
It is given that x = 1.5 and the break lasted for 0.5 hour, so
y = 4 - 1.5 - 0.5 = 2.
Using the result of part (a), at 1 p.m. Jenny's position is 5(1.5) - 5(2) = -2.5 km relative to her home. That is, she was 2.5 km to the north of her home.