How many trips has Earth made around the Sun in 8 mar years

The answer is; 15 years

It takes 687 days for mars to orbit the sun once. 8 mars years would, therefore, mean;

8 * 687 = 5496 days

The earth takes 365 days to orbit the sun once. Therefore, the earth will orbit the following number of times in 8 Mar years;

5496/365 = 15.058

Which is approximately 15 years