Two baskets together have $640$ oranges. If $\frac{1}{5}$ of the oranges in the first basket are taken to the second basket,the number of oranges in both baskets becomes equal. The number of oranges in the first basket is:

$(21.98)^{2} - (25.02)^{2} + (13.03)^{2} = ?$

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.

$2^{16}-1$ is divisible by

The difference between the squares of two consecutive numbers is $35.$ The numbers are

$A$ number exceeds its two-fifths by $75$. The number is: