Answer:
3 m, 7 m, 3 m, 7 m
Step-by-step explanation:
The perimeter is the sum of the side lengths, so the perimeters of your quadrilaterals are ...
6 m + 5 m + 4 m + 6 m = 21 m . . . . ≠ 20 m
7 m + 4 m + 4 m + 6 m = 21 m . . . . ≠ 20 m
3 m + 7 m + 3 m + 7 m = 20 m . . . . . This is it!
6 m + 3 m + 5 m + 5 m = 19 m . . . . ≠ 20 m