Simplify : $$ {(7) ^{2} ÷(7^{1\over 2})^{4}}$$

If (a + b):(b + c):(c + a) = 7:6:5 and a + b + c = 27, then what will be the value of 1/a: 1/b :1/c?

Simplify : $$ {(2x)^{2}-(2y)^{2}-(4x)^{2}}$$

What is the value of $$ {0.55 × 4.5\over 0.81}$$ ?

If $$ {\sqrt{1+{473\over{256}}}=1+{x\over 16}}$$ then what does x equal to ?

Simplify the following equation
$$ {\sqrt{(1-sin^{2}θ) ÷{(1-cos^{2}θ)}}}$$

$$ {4\over 5}×[{1\over 2}\ of\ 25]+12÷{3\over 4}-32=?$$

The Value of $$ {\sqrt{6-\sqrt{17-2\sqrt{72}}}}$$ is closest to: