You could respond with something supportive and encouraging. Here’s an example:
"Hey [Classmate's Name], I totally relate to what you're saying! It can be so tough to get started on math assignments, especially when the material feels complicated. It sounds like you have a good strategy with motivating yourself to tackle the work early in the week. Once you dive in, it really can be easier than it seems! Maybe we can study together sometime? It might help keep us both motivated. Keep up the great work, and remember, you're not alone in this!"