Note: I'm not doing eng, however I HAVE done the science equivalent units for ENG1091, and the first half of ENG2091. The first unit is the mathematics for engineering unit you will take regardless of which stream of engineering you do, and the second is done in every stream except electrical systems (although it really makes no sense to me that it's not, given the importance of vector calculus in electrodynamics... I'm guessing that stuff is covered in ENG2092, which I've also done the equivalent second half of.

But, I digress)
First off, let me say this - you might not be happy with your score, however a 30 is exactly average. You are quite literally sitting on a score where 50% of the cohort got a score above you, and another 50% got a score below. This might not excite you, however to me that says you're competent and capable - so don't stress.
Now, that's what I think, but here's what Monash thinks - to do ENG1091 (which is what you'd be looking at next year), the handbook only says you need to have done specialist maths. To do the science equivalent, MTH1030, you need a 30 in specialist maths. So as far as Monash is aware, you are prepared to undertake the next step in mathematics.
If you're still not convinced, let me share a couple of anecdotes: I got a 35 in specialist, and was over the moon. This was high enough to even do the "advanced" variants of the mathematics units, so I decided to try them out. However, when I say high enough, I was literally on the edge - you needed a 35 or higher to get into them. Now don't get me wrong, I'm capable, however throughout all of year 12 I would've spent about 3 hours a week going through questions with my teacher, and making sure I understood the theory. Coming into uni, I did not have this same support.
However, despite this setback, I walked out of the unit with an incredible 87% - which is still my second highest score. I got a score that beat people who had completely smashed me in specialist - including some who had smashed me (gotten a 48) and did the normal mathematics variant of the unit instead of the advanced. What this taught me, and hopefully you can take away from this as well, is that university is nothing like high school. You cannot use your high school marks to try and predict how well you do at university - so instead, you should just charge forwards and hope for the best. You won't have the same support from teachers, no - but I think you'll find that with some effort and dedication, you will surprise yourself.
Anyway, that's my opinion.
