Assume that the time to reach the barracks = 1 hr:
General = 10km/hr
troop = 6km/hr
Assume that the general is going from barracks to makati:
Get the intersection of the general and the troup:
6km = r1t1 + r2t2
since t1 = t2
6km = 10km/hr (t) + 6km/hr (t)
t = 3/8hr
get the distance travelled by the general after 3/8 hr:
3/8hr * 10km/hr = 15/4km
get the distance travelled by the troop after 3/8 hr:
3/8hr * 6km/hr = 9/4km
it would be like this:
<-------------------------6km----------------------------------------------->
<---troop=9/4km--><------------general=15/4km---------------->
get the time for the general to reach makati:
(9/4km) / (10km/hr) = 9/40 hr
get the time remaining after he arrive at makati:
9/40hr + 3/8hr + x = 1
x = 3/5
multiply the time remaining to the rate of the general and divide it by two since it is equal to length of the troop:
3/5hr * 10km/hr = 6km/2 = 3km
final answer = 3km