Your teacher is giving a test worth 200 points. There is a total of 30 five-point and ten-point questions. How many five-point questions are on the test?
Let x be the number of five-poin questions
Then the number of ten-point questions is 30-x
So....using [the number of questions] * [point value each] = total points, we have
x * 5 + (30 - x) * 10 = 200
5x + 300 - 10x = 200 simplify
-5x + 300 = 200 subtract 300 from both sides
-5x = -100 divide both sides by -5
x = 20 = number of five-point questions