Помогите пожалуйста с 66 и с 68

84 дм = 840 см = 8м 4дм

(1/8 + 2/9 - 1/4) * 5 1/7 : (7/9 - 2/3 + 1/6) = 1 4/5 1) 1/8 + 2/9 = (9+16)/72 = 25/72 2) 25/72 - 1/4 = (25-18)/72 = 7/72 3) 7/9 - 2/3 = (7-6)/9 = 1/9 4) 1/9 + 1/6 = (2+3)/18 = 5/18 5) 7/72 * 5 1/7 = 7/72 * 36/7 = 1/2 6) 1/2 : 5/18 = 1/2 * 18/5 = 9/5 = 1 4/5

5x-15y+8x+10y
=5x+8x-15y+10y=
=13x-5y

3691,6319,1963,9136 вот и всё