13 subtracted from 12 = 1
250
-1
13
13
25/40 - 12/40 = 13/40
-3
67
-6
13
62
6 x 12 is multiplied to get 72 4 is subtracted from 72 to get the answer 68
well you can put 1 1/12 into an improper fraction as 13/12 and make 2/3 into 8/12. so now your equation is 13/12 - 8/12 (much simpler!) which can easily be subtracted to be 5/12