You could also simply test the answers:
Start with answer b) 146
146=4x
x=36.5 --> way too long if the perimeter of the small rectangular is 30 only
secondly, test answer d) 50
50=4x
x=12.5 --> Correct!
12.5*2=25; 2.5*2= 5 --> sums up to 30
Start with answer b) 146
146=4x
x=36.5 --> way too long if the perimeter of the small rectangular is 30 only
secondly, test answer d) 50
50=4x
x=12.5 --> Correct!
12.5*2=25; 2.5*2= 5 --> sums up to 30
