x*y= 8 ... (i)
x2y + x y2 + x + y= 54 ... (ii)
If x*y = 8
Then, x2y = 8x [multiply x in both the sides of equation 1]
& x y2 = 8y [multiply y in both the sides of equation 1]
Thus, equation 2 can also be written as,
8x + 8y + x + y = 54
=> 9x + 9y = 54
=> x + y = 6
Now,
(x+y)2 = (6)2
x2+ y2 + 2xy = 36
Therefore x2 + y2 = 36- 2*8 ie. 20