Răspuns:
Explicație pas cu pas:
a)
P = 2 x (L + l)
L + l = P : 2 = 120 cm : 2 = 60 cm
L + L - 12 cm = 60 cm
2 x L = 72 cm
L = 72 cm : 2 = 36 cm
l = 36 cm - 12 cm = 24 cm
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b)
P = 2 x (L + l)
L + l = P : 2 = 56 cm : 2 = 28 cm
L + 3L/4 = 28 cm
7L/4 = 28 cm
L = 4*28cm/7 = 16 cm
l = 16 cm x 3/6 = 12 cm