Final answer:
To calculate the percentage of racers who did not complete the marathon, add up the number of racers who gave up and were disqualified, and divide it by the total number of racers who started the marathon. In this case, the percentage of racers who did not complete the marathon is 11.9%.
Step-by-step explanation:
To calculate the percentage of racers who did not complete the marathon, we need to add up the number of racers who gave up and were disqualified, and divide it by the total number of racers who started the marathon. In this case, there were 18 racers who gave up and 7 racers who were disqualified, so the total number of racers who did not complete the marathon is 18 + 7 = 25. The total number of racers who started the marathon is 210. To calculate the percentage, we divide 25 by 210 and then multiply by 100. So, the percentage of racers who did not complete the marathon is (25 / 210) * 100 = 11.9%.