Подобные слагаемые: а) -5k+12p-8k-13p+7k б) -1/6х+1/3х+1/9х-1/2х

-5k + 12p -8k - 13p + 7k = 2k - 8k - p = -6k - p
-1/6x + 1/3x + 1/9x - 1/2x = -1/6x +2/6x -3/6x  +1/9x = -2/6x + 1/9x = -1/3x + 1/9x = 1/9x - 3/9x = -2/9x