Răspuns :
lungimea = a
latimea = 3a/4
( a + 3a/4 ) x 2 = 42
7a/4 = 42 : 2
7a/4 = 21
a = 21 x 4 : 7
a = 12
lungimea = 12 cm
latimea = 3/4 x 12 = 14 : 4 x 3 = 9 cm
latimea = 3a/4
( a + 3a/4 ) x 2 = 42
7a/4 = 42 : 2
7a/4 = 21
a = 21 x 4 : 7
a = 12
lungimea = 12 cm
latimea = 3/4 x 12 = 14 : 4 x 3 = 9 cm