1. Put the given equation equal to t. Cubing both sides, u'll get
40 + 6t = t3. So, t3 - 6t - 40 = 0. Now solve the equation to get t=4.
2. x + y + 90 / xy = 1
or, x - xy + y = -90
or, 1 + (x-1) (1-y) = -90
or, (1-x) (y-1) = -91 = (-13) . ( 7)
So, x -1 = -13 and y - 1 = 7 and therefore, x = 14 and y = 8.
So, x + y + 2 / 4 = 14 + 8 + 2 / 4 = 6
3. I am not sure about the third question. I tried it but sry. Yeah, but i solved it in 2 sec using hit and trial method, i.e. x and y = 1 and 2.
And so ur answer would cum out to be 9.