Question 1131606
30 minutes = 1/2 hour, or 0.5 hour
d = 5(t)  
d = 4(t + 0.5)
.
5t = 4(t + 0.5)
5t = 4t + 2
t = 2
. 
d = 5t = 5(2) = 10 km
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Check:

5(2) = 10
and
4(2+0.5) = 10 Correct