Question 303837
Well let us look at it as 10 questions worth 10 points each. To score 80, 8 questions must be correct. Lets look at each question being 10 points. For the first question there a 10 possible questions for the second if you observe clearly there are 9 next one their are 8, etc etc:. Let z be the number of possible 8 questions selected. Then:

z = 10+9+8+7+6+5+4+3
z = 52