I need a formula. At a math contest,12 problems were given. Five points were awarded for each correct answer, and two points were deducted for each incorrect answer. Matt's score was 39. How many correct answer did he have

Answer 1

If he answered all 12 questions, and got x of them correct, then

5x - 2(12-x) = 39

Answer 2

5-2(12-5)=39
5-24+2=39
7=63
9
Am I doing this right

Answer 3

assuming some invisible x's, you are correct.

Answer 4

well done