1). -2/7 + 5/6= 2). -23 1/2 + 8 7/8= 5) x+(-6,3), если x= -18,1; x=3/8. 6) -5 1/9 + 6,4 - 2 5/7 + 1 2/3

1) -2/7 + 5/6 = 5/6 - 2/7 = (5 * 7 - 2 * 6)/42 = (35 - 12)/42 = 23/12 = 1 11/12 ;Ответ : 1 11/12 . 2) -23 1/2 + 8 7/8 = 8 7/8 - 23 1/2 = 71/8 - 47/2 = (71 * 1 - 47 * 4)/8 = (71 - 188)/8 = -117/8 = -14 5/8 ;Ответ : -14 5/8 .5) Если х = -18,1 , тогда x + (-6,3) = -18,1 + (-6,3) = -18,1 - 6,3 = -24,4;Если x = 3/8, тогда х + (-6,3) = 3/8 + (-6,3) = 3/8 - 63/10 = (3 * 5 - 63 * 4)/40 = (15 - 252)/40 = -237/40 = -5,925 ;Ответ : -24,4 и - 5,925 .6) -5 1/9 + 6,4 - 2 5/7 + 1 2/3 = 1 2/3 - 5 1/9 - 2 5/7 + 32/5 = 5/3 - 46/9 - 19/7 + 32/5 = (5 * 3 - 46 * 1)/9 - (19 * 5 + 32 * 7)/35 = -31/9 - 319/35 = (-31 * 35 - 319 * 9)/315 = (-1085 - 2871)/315 = 3956/315 = 12 176/315.Ответ : 12 176/315 .