Should I take a math SAT Subject Test?

Is it necessary for me to take a math SAT Subject Test if I got a 780 on the math section of the SAT and a 35 on the ACT math?

It depends on your college list and your potential major. If you are planning on any STEM major, and the college requires Subject Tests, then yes, you should take it. If you’re planning a humanities major, then it’s probably not necessary.