Total people in the survey = 50*3 = 150 people
people saying vanilla = 13+12+15 = 40
% of people choosing vanilla = 40/150 * 100 = 26.67%
If 2300 people were taken as sample
People choosing vanilla will be = 26.67/100 * 2300 = 613 people
Answer is 613,
Hope it helps!