Since you didn't give me a total # of questions on the test, I can't give you a direct answer....
But I can walk you through.
In math, "of", means you have to multiply.
80%= .8 This is bc 100% is = 1.00. () mean times or multiplied by ==================================================================== So you would do .8(how ever many total questions were on the test) Whatever # you get is the answer.