Getting high marks in so labelled 'difficult subjects' doesn't necessarily correlate to a high degree of intelligence, it only implies that you knew enough to score well in that particular test, nothing more than that. You can't justly infer that you're 'smart' because you get 95+% in physics or...
For Q2, then answer can't be (b) because Jane never followed that specific conclusion, i.e. 'Jane started to weigh herself daily in order to lose weight', so that implies that she inferred from the report that simply weighing herself daily will cause weight loss, which is obviously incorrect...
Read through the theory, do some of the easier questions, most of the development questions, and you should be absolutely set (assuming that you're actually decent at maths). Then practice with a few past papers and you'll be fine.
After practise, using the quadratic formula will be a breeze. Plus you could probably do it in your head after a while, if you're good at that sort of stuff.