1. The problem is to simplify the expression after the term $28k + 7$. 2. We start by factoring the expression $28k + 7$. 3. The common factor of both terms is 7, so we use the distributive property: $$28k + 7 = 7 \times 4k + 7 \times 1 = 7(4k + 1)$$ 4. This means the expression $28k + 7$ can be simplified to $7(4k + 1)$. 5. Factoring helps to see the structure of the expression and can be useful for solving equations or simplifying further.