I have A+ in 4 subjects and one B in other subject…I was wondering if the universities consider only best marks or there is something else?
They consider all the marks, but if the B grade is in a subject in which you will not be taking classes in college, or an ‘imposed’ subject (like Religious Studies in some countries), it won’t be considered on par with the other subjects.
It will if it’s a core subject.
As mentioned above, grades in all core subjects will be considered.
@skieurope
What if you plan to major in Creative Arts/ Writing but you are forced to take Math , and have a slightly lower grade in it?
Math is still counted.
@hezekiel is there no system of best 4 or something?
No. Nothing of that sort. What are the subjects you are talking about, and what is your prospective major?
No. You can continue to rephrase the question all you want, the answer is still the same.
I am thinking to take up physics as a major and astronomy as a minor!! I got a B in chemistry 
If you have all As in other core subjects, including math, physics etc., that ONE B in a core subject isn’t going to keep you out of any but the most selective schools (which are reaches even for those without a B on their transcript.)
All the grades you had in the past 4 years count (except physical education). You also need test scores and extra curricular activities showing who you are beside a good student.
Do you have money? Can you afford 48k~65k per year?
You need to bring specifics to this forum to get answers, you are wasting everyone’s time.
We will need GPA through your Jr. Year, SAT/ACT scores, Tofel(if required), ECs, list of target schools and more importantly, if you are full pay or need aid if you need aid how much you or your parents can pay.