877 to binary, octal, and hexadecimal

Our number system is in base 10, which means that each digit has a value that is a multiple of 10.

For ex:
877 literally means
8  7  7   where each digit is multiplied by
10^ 2   10 ^1   10^0  respectively
which is 8 * 10^ 2 + 7 * 10^1 + 7 * 10^0 = 8 * 100 + 7 * 10 + 7 * 1 = 800 + 70 + 7 = 877

Binary is in base 2, so each of its digits (which can only be 0 or 1) are multiplied by multiples of 2 (2^0, 2^1, 2^2 ect.)

To find what 877 is in binary you can do the following:
the symbol : means divide and i'll write the quotient + the remainder

877 : 2 = 438 + 1  (438 is the quotient, 1 is the remainder)
438 : 2 = 219 + 0
219 : 2 = 109 + 1
109 : 2 = 54 + 1
54 : 2 = 27 + 0
27 : 2 = 13 + 1
13 : 2 = 6 + 1
6 : 2 = 3 + 0
3 : 2 = 1 + 1
1: 2 = 0 + 1

now write ALL off the remainders from BOTTOM to TOP:
1101101101

use a similar step for octal (use 8 instead of 2 as the divisor) and hexidecimal (use 16 instead of 2 as the divisor) 

21, i'm pretty sure it's right lol