michael has 30 balls,yellow blue green black.25 balls are not yellow,8 are black,16 are not green how many blu balls are there

Let:

t = total no. of balls

y = no. of yellow balls

b = no. of black balls

g = no. of green balls

B = no. of blue balls

[tex]y = t – 25 = 30 – 25 = 5 \\ b = 8 \\ g = t – 16 = 30 – 16 = 14 \\ t = y + b + g + B \\ 30 = 5 + 8 + 14 + B \\ B = 3[/tex]