Twenty seamstresses sew shirts for a clothing manufacturer and are grouped according to how many shirts per day each one can sew. seamstresses in group 1 can each sew 12 shirts per day and those in group 2 can each sew 15 shirts per day. together the seamstresses can sew 279 shirts per day. how many seamstresses are in group 1? a) 7
b) 9
c) 11
d) 13

It depends on the subject for me. some exams are easier than others so i usually go through it and answer questions i know based on my general knowledge, then double check after. going through the lesson can a lot  because the exams can be  very lesson-specific, but sometimes they are ridiculously long so a lot of people don't take the time. i did find that, when i went through the lessons, i was making 100's on my exams vs strictly using + the internet and  i make 90's.