Answer: 4200
Assuming that this question is based on a graph, and that this graph tells us that people 50-64 years make up 35% of all the voters, then it would mean that
35%of 12000= 35/100 * 12000= 35 * 120= 4200
So, assuming that people at age 50-64 make up 35% of the voters, then 4200 of them voted.