Some thoughts:
1. *High* quality questions are not the norm. They are rare, and that's what happens when people are learning mathematics. Asking good question is remarkably difficult, and we shouldn't be worried that a question is not "high quality". I think sometimes, out of the good intention of "making the site better", we may be forgetting about the place where we were when we started learning.
2. The OP says they tried a few binomial identities to no avail. Sometimes users are truly cluless about what to do, and maybe it is not a bad idea to engage in the comments first before laying…