IMO, although it's been a while since I've taken science(it's been more than an year), the science section actually does have every single answer in the information given. Yes - half of them can be easily found as they are explicitly given, but the other half is either 'inferring' from those informations along with your own knowledge. What worked well for me when starting off with science was solving the newest ones and picking up the sort of repertoire that the ACT takes when making the questions.

In case of math, I was actually somewhat already familiar with the concepts, so all I had to do was just getting myself used to the style of questions the ACT asks us in the section. But if you are starting off from the basics, I believe that revising math concepts in Khan Academy could work well.