svetazuna (5/6x + 1/7x) *42 = 5/6х * 42 + 1/7х * 42 = 5*7х + 6*х = 35х + 6х = 41х,

или:

(5/6x + 1/7x) *42 = (35/42х + 6/42х) * 42 = 41/42х * 42 = 41х

vochgamep6i43u (5/6x + 1/7x) *42 = 5/6х * 42 + 1/7х * 42 = 5*7х + 6*х = 35х + 6х = 41х,