.
The problem's wording makes me shudder - so unprofessionally it sounds.
The normal mathematical formulation should sound this way
Find integer numbers b such that (b+6) divides (5b+6) with no remainder.
The "bases" are irrelevant.
All these tricks with "divide into" were used at the times of Shakespeare and Dickens.
It is just 100 years nobody uses such outdated form in mathematical texts,
excluding the lovers of old English, who want to show in this way how smart they are.