text: using clock arithmetic (12 hour clock) find the following difference:? 4-9? please explain this to me! thanks! four o'clock minus nine hours... 7 o'clock.  4-1 =3 4-2 =2 4-3 =1 4-4 = 12(on the clock) 4-5 =11 4-6 =10 4-7 =9 4-8 =8 4-9 =7