Answer:
13
Step-by-step explanation:
there is a rule that says that if you add any 2 sides, it should be more than the third. 9+21 is greater than 13. 21+13 is greater than 9. 13 is the only number which if you add 9 to it it will be greater than 21. 12 will equal 21, but it still wont work.
hope this helps :))
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Length: w+4
Width:w
Perimeter:44
Area: L times w
P=44
44=2(w)+2(w+4)
44=2w+2w+8
44=4w+8
36=4w
w=9
L=w+4
L=9+4
L=13
Area should equal 117 cm squared