1/10 people who do a 3/4 subject get 40+. Hence, 9/10 of people find it too hard; hence, for the 'average' person (whatever that means

) it is very difficult. It's such a subjective question, as it varies so much from person to person. It depends on a few things, some of which you can change and some of which you can't:
a. Your intelligence/abilities (or whatever you want to call it).
b. How hard you're willing to work.
c. Your life circumstances at the time.
d. Your overall mindset (how high you aim, whether you believe in yourself, ability to cope with stress etc.)
e. Your school, cohort, teacher etc. Though I like to believe that no matter what school you're at you can achieve if you rely on yourself rather than others to achieve for you.
If you work hard but don't have a. and c. in your favour, then you have very little hope of a 40+. Sorry, harsh but the fact is that only 1/10 of people do achieve it! If everyone state-wide started working three times as hard, still only 1/10 would achieve it.
However, the very fact that you're part of the AN community and are clearly working hard and aiming high in year 10 suggests that a., b. and d. are likely to be in your favour. If that's the case, then I agree, with
consistent hard work, you should be fine with achieving it.
(P.S. Hope nothing in this sounds arrogant - unintentional if so

).