The weight of a bucket full of water is 36 kg. If the weight of a half-filled bucket is 21 kg, what will be the weight of the empty bucket?

In a group of 15 women, 7 have nose studs, 8 have ear rings and 3 have neither. How many of these have both nose studs and ear rings? 

If 2x + 3y - 5z = 18 , 3x + 2y + z = 29 and x + y + 3z = 17 , then what is the value of xy + yz + zx ? 

If 12x – 15 y =9x + 5y, the value of $$ {x^{2}+{y^{2}}\over{x^{2}-y^{2}}}$$ is

If 0.5x + 0.7y=0.5 and 0.7x + 0.5y=0.7,then the value of x+y is

If $$ {(x-2)^{2}+(y-{1\over2})^{2}}=0$$, then the value of $$ {x\over y}$$ is

$$\sqrt{x}÷ \sqrt{144} = 0.02, $$ then the value of x is 

Direction : What should come in place of the question (?) in the following question.

$$ {\sqrt{441}}+ {(71)^{2}} -{(?)^{2}}=2707 $$