Please help me......

Solution : 

(a)


(b) From graph we can conclude,
v = d/t
v = 10 km/30min => 10 km/ 0.5h
v = 20 km/h
So, distance covered by bus in 15 min 
d = 20 × (15/60)
d = 5km
So, 
Distance covered by the bus at 3.15pm is
=> Distance covered by bus at 3.00 pm + distance covered by bus in 15 min
=> 20 + 5
=> 25 km