Answer: He is idle for 8.4 hours.
Step-by-step explanation:
Since we have given that
Number of hours he repairs =30 hours
Percentage of hours he worked = 72%
Remaining percentage of hours he remains idle is given by
[tex]100-72\\\\=28\%[/tex]
So, Number of hours he is idle for a driving is given by
[tex]0.28\times 30\\\\=8.4\ hours[/tex]
Hence, he is idle for 8.4 hours.