So I would start this off by plugging in the variables into side B. So if we were to plug 7 into B there would be 22 meters left of the perimeter. Therefore meaning 22 between A and C. Now A is 3 meters shorter than TWICE of B. So 7 times 2 is 14 and 14 minus 3 is 11. now we have 11 and 7 which equals 18. 29 minus 18 giving us 11 left. 11 is C. Now it says c is 4 meters longer than B so it 7 plus 4 is 11. And everything adds up. HOPE THIS HELPS.
Plane averaged 88mph with the wind and 44 against the wind. the average of these two averages is 66 mph. plane speed in still air is 66 and the wind speed was 22 (88-22=66 and 44+22=66)