Răspuns :
lungimea = x
( x + 7 ) x 2 = 42
x + 7 = 42 : 2
x + 7 = 21
x = 21 - 7
x = 14
lungimea = 14 cm
( x + 7 ) x 2 = 42
x + 7 = 42 : 2
x + 7 = 21
x = 21 - 7
x = 14
lungimea = 14 cm