a)
lungimea = a
latimea = 2a/3
( a + 2a/3 ) x 2 = 30
a + 2a/3 = 30 :2
a + 2a/3 = 15 /x3
3a + 2a = 45
5a = 45
a = 45:5
a = 9
Lungimea = 9 cm
Latimea = 2/3 x 9 = 9 :3 x 2 = 6 cm
b)
lungimea - a
latimea = 2a/5
( a + 2a/5 ) x 2 = 14
a + 2a/5 = 14 : 2
a + 2a/5 = 7 /x5
5a + 2a = 35
7a = 35
a = 35 :7
a = 5
Lungimea = 5 cm
Latimea = 2/5 x 5 = 5:5 x 2 = 2 cm