1.
x^2/3 - x - 6 = 0
x^2 - 3x - 18 = 0
(x - 6)(x + 3) = 0
x = 6 or - 3.
2.
3m^2 + 25/3 = 10m
9m^2 - 30m + 25 = 0
(3m - 5)^2 = 0
m = 5/3.
3.
(a) Since product of roots = - 28, so possible roots are :
1, -28 or - 1, 28
2, -14 or -2 , 14
4, -7 or - 4, 7
So possible sum of roots are :
+/- 27, +/- 12 or +/- 3.
(b) So possible values of k are also +/- 27, +/- 12 or +/- 3.
But k is a natural number, so k can be 3, 12 or 27.