Here we go!
I don't know if Brazil is like the US when it comes to the battle of Church vs State. Many (but not all) religious people would like religion to be incorporated into the lives of everyone, including our school systems and government. However the concept of "America" was inspired and created upon the idea of separation of church and state, although they aren't completely separate now, and never were separate in the past. There has been a constantly growing movement towards Politically Correctness (PC = politically correct). Nowadays, being PC is fundamental if you want support from many people. If you are running for presidency, and you announce to the nation that you don't think that women should have the right to vote, you are not PC and will not get elected.
Now, before I continue I have to mention this... a long time ago when I was in elementary school (when I was 11), every day at school we had to say the Pledge of Allegiance while facing towards the US flag (every classroom had one). The Pledge of Allegiance goes like this:
I pledge allegiance to the flag
of the United States of America
and to the republic for which it stands,
one nation under God, indivisible,
with liberty and justice for all.
As far as I know, children still say it, but I don't think they are required to say it if they don't want to. In the past 8-10 years there have been several cases involving the US Supreme Court (the top of the judicial 'food chain') regarding whether or not it is unconstitutional to require children to say "one nation under God". This is another battle of Politically Correctness that never needed to be fought if the politicians had simply kept church separate from state (public schools are funded by state taxpayers which is the reason why people can argue about these issues).
That is one side of the issue, the other is the debate about Religion versus Science (or Math in this case). The major argument made against Religion is that there is no proof for any of the claims made in the bible, and that it's contents must be accepted based on faith alone, not evidence. However, in Science, EVERYTHING is based on evidence and everything can be broken down into simpler concepts which have been proven through testing. At the most fundamental level of Math is Addition.
It is generally accepted that 1 + 2 = 3. The satire from that cartoon comes from the fact that children are taught Math concepts as facts, and Religion concepts as facts, since they both come from a book. But the twist is that the 'facts' that come from Math books are backed by evidence and years of testing and proof, while the 'facts' from Religion books are not.
So this cartoon is not just a 'cute joke' but it's also a hidden criticism of both 1) politically correctness of the education system, and 2) what constitutes fact... we believe something that we read in a book, but if you can't 'read between the lines' and think about whether the book is based on evidence or made-up stories, then you will never know what's real and what's not.
Earlier I said the cartoon was 'funny, but wrong'. I meant that the idea of Math being a religion and not based on truth - that is wrong. I love Math.
It's strange to think about, but a tiny little cartoon like that is actually criticizing how the majority of society thinks! But it would be difficult to know that unless you understand how this society thinks.