First, I'll calculate the percentage:
\(\frac{12}{30} *100%= \frac{12*100}{30} = \frac{120}{3} =40\)
so it was 40 % of people that chose blue
And now we can calculate the angle;
the full chart would have 360 Degrees, and the "blue" portion of the chart would have 40 % od 360 or \(\frac{40*360}{100} =4*36=120+24=144\)
so the angle would be 144 degrees!