SOLUTION: A math test is worth 100 points and has 30 problems. Each problem is worth either 3 points or 4 points. How many 4-point problems are there?

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Question 701291: A math test is worth 100 points and has 30 problems. Each problem is worth either 3 points or 4 points. How many 4-point problems are there?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Hint:

x+y = 30 ---> y = 30-x

3x+4y = 100

3x+4(30-x) = 100

3x+120-4x = 100

solve for x, then use this to find y