б) $$10 \cdot (1,37k - 0,12k) : 5 : 8 = 0$$ $$10 \cdot (1,25k) : 5 : 8 = 0$$ $$12,5k : 5 : 8 = 0$$ $$2,5k : 8 = 0$$ $$0,3125k = 0$$ $$k = 0:0,3125$$ $$k = 0$$ Ответ: k = 0