If a³ – b³ – c³ – 3abc = 0, then 

$$ if \ {1\over x}+x=4,$$ then find $${1\over x^2}+x^2$$

If m + n = 1, then what will be the value of m³ + n³ + 3mn?

$$ {4\over 7}×{2{4\over 5}} ÷{2\over 5}=?$$

If 5x + 5 > 2 + 2x and 5x + 3 ≤ 4x + 5; then x can take which of the following values?

(0.85 % of 405 ) + (2.25 % of 550 )=?

$$\left({?-0.5\over 0.2} \right)={120\over 2}$$

$${\sqrt{4×?}}={160\over 10}$$