3/5 * 7/9 - 3/5 * (7/9 - 5/6)=

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3/5 * 7/9 - 3/5 * (7/9 - 5/6) = 3*7/5*9 - 3/5 * (7*4/9*4 - 5*6/6*6) == 21/45 - 3/5 * (28/36 - 30/36) = 21/45 - 3/5 * (- 2/36) = 21/45 + 3/5 * 2/36 == 21/45 + 3*2/5*6 = 21/45 + 6/30 = 21*2/45*2 + 6*3/30*3 = 42/90 + 18/90 == 60/90 = 6/9 = 2/3