Solution step by step ? 2 / A + 1 , + 5 = 12 / A + 1?

First you have to learn correct presentation. One misspelling ruins the entire statement.

Everybody knows that + means plus, / means a fraction, and = means equal. Use the symbols with confidence. I mean without explanations.

We use parentheses any time we need to explain what is treated as a unit. You might have meant (2/A) + 1 or 2/(A + 1) and there is no way to guess which is correct. Get the presentation right and this is easy to work out.