1) 15th June 2014 - 25th Oct 2015 - Part time : worked varies from 20 - 30
To calculate the full-time equivalent (FTE) of part-time work, you have to add up all the hours and divide by 30 - literally you will have to go back and find the exact hours worked per week (or use the # provided on your Letter of Employment, as long as it is fairly close).
Unfortunately, working a part-time job at the same time as a full-time job gets you nothing additional beyond the "full-time" credit. So when calculating the full-time equivalent, you exclude the time that overlaps with your full-time job.
Just as an example, I'll assume 25 hours every week -
From 15th June 2014-17 Aug 2014 - this is 8 weeks, so 25 hours per week * 8 weeks = 200 PT hours.
From June 14 2015 - Oct 2015 is 15 weeks * 25 hours per week = 375 PT hours,
Total of 575 PT hours / 30 = 19 weeks FTE (I'm rounding down).
2) 18th Aug 2014 - 13 June 2015 - Full time : 40 hours per week.
= 47 weeks of full-time employment
3) 2nd Dec 2014 did you mean 2015?- 24th Dec ( Job is Current and Continuing to work here ) : 40 hours per week
Assuming you meant 2015 - I'll say 3 weeks.
All 3 jobs combined:
19+47+3 weeks = 69 weeks, credit for 1 year of experience.