=(7/12 - 4/12) * 16/19 = 3/12 * 16/19 = 1/4 * 16/19 = 4/19
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=(7 9/15 - 2 4/15) * 9/32 = 5 1/3 * 9/32 = 16/3 * 9/32 = 3/2 = 1 1/2
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=(11/24 +4/24) * 1 3/5 = 15/24 * 8/5 = 3/3 = 1
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=(6 16/16 - 2 5/16 ) *4/25 = 4 11/16 * 4/25 = 75/16 * 4/25 = 3/4