1) Addressing the problem 2) At work at an assignment 3) Attacking the problem 4) Attending to a task 5) Attending to the assignment 6) Attending to the case 7) Attending to the matter 8) Attending to the task 9) Busy at a task 10) Consider the job done 11) Consider the task done 12) Dealing with the matter 
Drinking alcohol (Scottish slang). Example: We're onit tonight at the bar.