I am assuming that this question is a non-calculator question. In that case, an easy and basic way to calculate these percentages would be to spilt up the percentages.

First of all for 15% of 8200km, the first thing that you could do is find 10% of 8200km. 10% of 8200km can be found by dividing it by 10 which would just be 820km. Then we can find 5% of 8200km by dividing the 10% we just found by 2, giving us 5% which is 410km. Then we can add up our results of 10% and 5% to give us 15%. This would be 820 + 410 = 1230km.

Next for 65% of 240. Again we would split up the percentages. First of all we can find 50% of 240 by just dividing by 2 which would give us 120. Then we can find 5% of 240 by diving our result of 50% by 10 which would give us 12. Then to find 10% we can just double our result of 5% to give us 24. Finally we would add up our 3 percentages of 50%, 5% and 10% to give us 65% which would be 120 + 12 + 24 = 156.

Finally for 45% of 180. The first thing to do would be to find 50% of 180 by just dividing by 2 which would give us 90. Then we can find 5% of 180 but just dividing our result of 50% by 10 which would give us 9. Then we can take away our result of 5% from 50% to get 45% which would be 90-9 = 81.