Б) 7/11 : 4/5 = (7*5)/(11*4) верное равенство
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а)
1/13 : 7/13 = 1/13 * 13/7 = 1/7
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б)
2 7/10 : 1 5/100 = 2 7/10 : 1 1/20 =27/10 * 20/21 = 18/7 = 2 4/7
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г)
= 2 1/4 : 7/8 = 9/4 * 8/7 = 18/7 = 2 4/7