Have you heard of the BODMAS / BIDMAS rule?
This rule changes your answer from 42 to 3 instead. that is because this rule says you need to follow a specific order when calculating. It seems easy but is quite easy to forget since we all want to start with the first number.
here the BODMAS stands for Brackets, Of/operations, multiplication, addition,Subtraction. if it's BIDMAS = same but I stands for indices.
So ,
13 - 3 × 4 + 2
=13 - 12 + 2 (multiply first)
=13 - 10 (add , don't forget its -12 +2)
= 3 (lastly we are subtracting)