How do I know which age group has about 3% of the male population?

Based on the given graph we have the following:
The age bracket 70-74 consist of 1.5% of the total population.
If the male population is 50%, then its percentage of the male population is
[tex]\frac{1.5\%}{50\%}=\frac{0.015}{0.5}=0.03=3\%[/tex]Therefore, the age bracket 70-74 consist of 3% of the male population.