The sum of seven numbers is $235$. The average of the first three is $23$ and that of the last three is $42$. The fourth number is

$73 \times 18 + 486 = ? + (13)^{2}$

$(8.5 \times 8.5 + 93.5 + 5.5 \times 5.5)^{1/2}$ is equal to ...........

$1599 \times 199 \div 49 - 1398 + 3877 = ?$

For any integral value of $n$,$3^{2n} + 9n + 5$ when divided by $3$ leaves the remainder:

The numerator of a fraction is the product of two numbers. One of the numbers is greater than the other by $2$. The greater number is smaller than the denominator $D = 7+c$ (where $c > -7$ is a constant). If the fraction is $f(x) = \frac{(x-2)x}{x+k}$ (where $x$ is the greater number),find the minimum value of the fraction.