250
а) 12,915 : (- 6,3) = - 2,05
б) - 0,8 : (- 2/15) = - 8/10 : (- 2/15) = - 4/5 : (- 2/15) = - 4/5 * (- 15/2) = - 2/1 * (-3/1) = 6
в) - 4 : 2/9 = - 4/1 * 9/2 = - 2/1 * 9/1 = - 18
251.
а) 5,4у = - 32,94
у = - 32,94 : 5,4
у = - 6,1
б) 7/9х + 11/12 = 13/18
7/9х = 13/18 - 11/12
7/9х = 26/36 - 33/36
7/9х = - 7/36
х = - 7/36 : 7/9
х = - 7/36 * 9/7
х = - 1/4