а)15 - 130= .б) 130+142 =. в) 0,8 1 - 19=. г) 17 5*4=.

а) 1/5 - 1/30 = 6/30 - 1/30 = 5/30 = 1/6
б) 1/30 + 1/42 = 7/210 + 1/210 = 8/210 = 4/105
в) 0, 8 - 1/9 = 8/10 - 1/9 =  72/90 - 10/90 = 62/90 = 31/15
г) 17/5 * 4/1 = 68/5 = 13.6