Ответ Автор - statas025 4) 5/7 -(21/4 -15/7 : 5/4) = 5/7 -(21/4 - 15/7 *5/4)= 5/7 - (21/4 -3/7 *4) = 5/7 - (21/4 -12/7 )= 5/7 - 99/28 = -79/28