1/11-1/33=? 7/11-7/12=? 13/30-2/45=? 7/15-2/5=? 13/60-7/40=? 11/21-3/14=?
1/11-1/33=3/33-1/33=2/33./// 7/11-7/12=84/132-77/132=7/132. 13/30-2/45=39/90-4/90=35/90. 7/15-2/5=7/15-6/15=1/15. 13/60-7/40=26/120-21/120=5/120=1/24. 11/21-3/14=22/42-9/42=13/42