(a + b)c = ac + bc - распределительное свойство умножения
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а) 51 * 3/11 + 51 * 8/11 = 51 * (3/11 + 8/11) = 51 * 11/11 = 51 * 1 = 51
б) 65 * 5/13 + 65 * 4/13 = 65 * (5/13 + 4/13) = 65 * 9/13 = 65 : 13 * 9 = 45
в) 13/17 * 13/19 + 13/17 * 4/19 = 13/17 * (13/19 + 4/19) = 13/17 * 17/19 = 13/19
г) 21/44 * 11/16 + 21/44 * 5/6 = 21/44 * (11/16 + 5/16) = 21/44 * 16/16 = 21/44 * 1 = 21/44
д) 100 * 7/20 + 100 * 3/20 = 100 * (7/20 + 3/20) = 100 * 10/20 = 100 * 1/2 = 100 : 2 * 1 = 50
е) 17/63 * 10/37 + 17/63 * 1/37 = 17/63 * (10/37 + 1/37) = 17/63 * 11/37 = 187/2331