From the bar graph, we find that the first two bars represent first 6 months from January to June.
The height of the bar gives the number of people who have their birthdays in those 3 months.
Jan, Feb and March (Number of people) = 12
April, May and June (Number of people) = 7
Therefore, the number of people who have their birthdays in the first 6 months = 12 + 7 = 19