5 1/6:4 2/15=31/6*15/62=5/4=1 1/4
3 1/6-1 1/4=3 2/12-1 3/12=2 14/12-1 3/12=1 11/12
1 11/12:30 2/3=23/12*3/92=1/16
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43/63-23/36=172/252-161/252=11/252
55/84:11/252=55/84*252/11=15
2 2/3:1 7/9=8/3*9/16=3/2=1 1/2
1 1/2+15=16 1/2