The picture below is a sample journal entry and response.
After assigning a journal entry, I use the math journal rubric (see picture below) to help me assign a grade for each journal entry. You can find a copy of the rubric here or by clicking on the "Engaging Math Activities" link of the "File Cabinet" on my blog.
In addition, I have created a Math Journal Rubric & Scoring Guide where I provide details about how to set-up math journals, general guidelines for implementing journals, and work samples to help you use math journals in your classroom. It is available here or at my Teachers Pay Teachers Store.