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 1

x+y = 30

3x+4y = 100

3x +4 ( 30 - x) = 100

3x + 120 - 4x = 100

-x = -20

x = 20

y = 10

20 of the 3 point problems

10 of the 4 point problems