How many numbers up to $100$ are divisible by $7$?

If the digit in the unit's place of a two-digit number is halved and the digit in the ten's place is doubled,the number thus obtained is equal to the number obtained by interchanging the digits. Which of the following is definitely true?

The sum of five consecutive even numbers of set-$A$ is $220$. What is the sum of a different set of five consecutive numbers whose second lowest number is $37$ less than double the lowest number of set-$A$?

$21.9 \%$ of $(511.987 - 42.49) = \frac{?}{5.5}$

$n$ is a whole number which when divided by $4$ gives the remainder $3$. The remainder when $2n$ is divided by $4$ is

$\frac{6}{5}$ of $\frac{3}{4}$ of $\frac{1}{2}$ of $? = 3600$