Basic Number Systems

Which of the following statements is true?

The greatest four digit even number that can be formed using the digits $7, 0, 6, 5$ without repeating the digits is

How many four-digit numbers can be formed using $7, 5, 0, 2$ only once in a number ?

Set of whole numbers is denoted by 

$1R6$ is a three-digit number in which $R$ is a missing digit. If the number is divisible by $6$, the missing digit is

If the sum of two numbers is considered as '$a$' and their product is considered as '$b$', then what will be the sum of their reciprocals?

$7X2$ is a three-digit number in which $X$ is a missing digit. If the number is divisible by $6$, the missing digit is

Digit $1$ is occurring $136$ times on writing all of the page numbers of a book. What will be the number of pages in the book?

${\left(170\right)}_{10}$ is equivalent to?

Convert the hexadecimal number ${\left(1\mathrm{E}2\right)}_{16}$ to decimal.

Convert ${10101}_2$ into octal number.

If $n$ is a natural number, then unit digit in $6^n-5^n$ is