Math is my weak subject too, I hadn't touched any of the concepts since high school so it was hard to get back into but it came more quickly as time went on. I don't know what the exact average is for SLP but I do know other departments at U of A use the minimum 50th percentile rule, so getting a bit higher than the cutoff scores should make you feel comfortable. I studied for a couple hours a day for about a month leading up to the test. I took notes on the entire Quant section review that the ETS website has up, it covers most of what you'll need to know. I didn't really study much for verbal besides reading novels with difficult language on my kindle and defining all the words I didn't know. There's lots of vocab flashcard apps too. I didn't study much for the writing section but my advice (for all sections!) would be to do practice exams. I ran out of time on one of the essays so I think I should have prepared more for that section. Hope this helps!