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(1/6-5/9)*(1/2-3/7)*7.1/5=(3/18-10/18)*(7/14-6/14)*36/5=-7/18*1/14*36/5=-7/224*36/5=-252/1120
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(1/6-5/9)*(1/2-3/7)*7.1/5=(3/18-10/18)*(7/14-6/14)*36/5=-7/18*1/14*36/5=-7/224*36/5=-252/1120