(3/4-4/5)×7,8-(2/3+4/7 )×(-7/13)

(3/4 - 4/5) * 7,8 - (2/3 + 4/7 ) * (-7/13) = 83/300,1) 3/4 - 4/5 = 15/20 - 16/20 = - 1/20,2) -1/20 * 7,8 = -1/20 * 78/10 = - 39/100  (или -0,39),3) 2/3 + 4/7 = 14/21 + 12/21 = 26/21 = 1 5/21,4) 1 5/21 * (-7/13) = - 26/21 * 7/13 = -2/3,5) -39/100 - (-2/3) = -117/300 + 200/300 = 83/300

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