We can employ a simple repeated decimal trick:
###
Alternatively, we can compute the partial sum of the series.
As 
, the second term vanishes and we're left with 
. Notice that this is really just a more formal version of the earlier trick.
Answer:
10
Step-by-step explanation:
if she runs 5 km in half an hour, she runs 10 in a whole hour.
4/5x-8=3
move -8 to the other side and add
4/5x=3+8
4/5x=11
move 5x to the other side and multiply
4=5x*11
4=55x
4/55=x
