Digits and digits

It is not easy to explain here but will try first make 17 places or dashes. and last digit 8

– – – – – – – – – – – – – – – – – – 8

...................................................................× 2

...................................................c/f

---------------------------------------------------------------- start multiplication

– – – – – – – – – – – – – – – – – – 8

...................................................................× 2

................................8 × 2 = 16.............c/f......... 1 write 6 in 10's place and continue

---------------------------------------------------------------- start multiplication

...................................................................... 6

– – – – – – – – – – – – – – – – – 6 8

...................................................................× 2

6 × 2 = 12 + 1 = 13.............c/f......... 1 write 3 in 100's place& continue

---------------------------------------------------------------- start multiplication

...................................................................... 6

continue multiplication and addition of c/f any till you get 8 in first position.

421052631578947368 × 2

= 842105263157894736

let $x$ be the number represented by all of the other digits before 8 in the original number. The original number is then $10x+8$ . The new number can also be represented in terms of $x$ by $x+8\times { 10 }^{ 17 }$ . Since the new number is twice the original, we can solve for $x$ from $2(10x+8)=x+8\times { 10 }^{ 17 }$ . After $x$ is found we add an 8 to the end of it to come out with the final answer of $\boxed{421052631578947368}$

abcdefghijklmnopq8

x..................................2

———————————

8abcdefghijklmnopq

Therefore q=6 (8x2=16) with a carry, p=3(6x2+1=13) with a carry, ...