Question

Ewa has 20 balls of four colors: yellow, green, blue, and black. 17 of them are not green, 5 are black, and 12 are not yellow. how many blue balls does ewa have?

Answer 1

20 total balls:

5 are black

17 NOT yellow

12 NOT green


20-17 = 3

20-12 = 8


5 Black + 3 yellow + 8 green = 16 balls


20 total balls - 16 balls = 4 blue balls



Ewa has 4 blue balls.