а) 2a + 3b - 5c = 2(2,4,3) + 3(-3,1,2) - 5(5,-2,-1)
= (4,8,6) + (-9,3,6) - (25,-10,-5)
= (4 - 9 - 25, 8 + 3 - 10, 6 + 6 - 5)
= (-30, 1, 7)

б) a + 4b + 12c = (2,4,3) + 4(-3,1,2) + 12(5,-2,-1)
= (2,4,3) + (-12,4,8) + (60,-24,-12)
= (2 - 12 + 60, 4 + 4 - 24, 3 + 8 - 12)
= (50, -16, -1)

в) 2a - 6b = 2(2,4,3) - 6(-3,1,2)
= (4,8,6) - (-18,6,12)
= (4 + 18, 8 - 6, 6 - 12)
= (22, 2, -6)

г) -7b = -7(-3,1,2)
= (21,-7,-14)

д) 5c = 5(5,-2,-1)
= (25,-10,-5)