I didn’t have to write this kind of essay when applying to grad school, but I’ve been a social worker for over 12 years, so here are my thoughts:
A phrase you’ll hear in social work is “case to cause”. It refers to the importance of moving from a focus on an individual’s personal stressors (ex., being homeless) to the social/systemic reasons for their stressors (ex., lack of affordable housing, underfunding of homeless shelters, etc). I imagine that the schools want to see if you can make this jump in perspective in your essay; that is, if you had “the power and resources” would you be able to conceptualize the systemic factors at work behind a social problem and be able to offer ways to address those factors.
I’m not sure, but I highly doubt they want you to come up with an original solution; likely they want to see if you can research, critically assess, and synthesize information about causes and current interventive models on a case and cause level, and to draw a conclusion from this about how you would approach the issue. That is, they likely want to see if you have the critical skills to think about problems systemically, to understand basic articles that are written from this perspective, and to ground your ideas in some basic research and reading. And, yes, you should credit all sources that you draw upon; it’s a basic requirement of any academic writing, and it will help your essay’s credibility.
Best,
Duck!