Question 896504
He works 9 hours.

Lets take time he spend for lunch is X.

Then time he spends for computing is 5X.

Lets get the filing time as Y.

So for writing .. he spends 2Y

And twice as lunch for filing. So Y =2X

So all these time should be equal to 9! hours.

Add them all

{{{X + 5X + 2X + 4X = 9}}} hours.

Lets convert it to minutes.

{{{12X = 9*60}}} minutes.

{{{X = 45}}} minutes 

Time he spends for each activity is as follows

Lunch 45 min
Computing 3h and 45min
Filing 1h and 30min
writing 3hours.