Binary is pretty simple.

Read from right to left the numbers in order of size (lowest -> highest).

The first digit represents 1s
The second digit represents 2s
The third digit represents 4s
The fourth digit represents 8s
....

and so on doubling each time. You then add up how many 1s, 2s, 4s, 8s, ... to convert to decimal.

To convert decimal to binary, what I do is use a system akin to "Russian Mathematics". Rewrite the number as x * 1, then halve one side and double the other...
Then check the odd numbers in the right hand column and rewrite :)

EG To convert 72 (decimal) into binary,

72 = 1 * 72
= 2 * 36
= 4 * 18
= 8 * 9
= 16 * 4 (ignoring the 1/2)
= 32 * 2
= 64 * 1

Then check the odd numbers (9 and 1) Then rewrite odd numbers as 1s and even as 0s. eg from top to bottom if the number is odd on the right hand side I put 1, and 0 for even: 1001000 (64 + 8)

The questions you pose give:

A= 01000001 = 65
B= 01000010 = 66

And I am not sure about that...