l = L - 25 si P = 2L + 2l ;
P + 38 = 2( L + L / 4 ) + 2l;
Ultima ecuatie devine 2L + 2( L - 25 ) + 38 = 10L / 4 + 2( L - 25 ) ;
4L - 50 + 38 = 5L / 2 + 2L - 50 ;
4L - 12 = 5L / 2 + 2L - 50 ;
2L - 5L / 2 = 12 - 50 ;
4L - 5L = - 76 ;
L = 76 ;
l = 76 - 25 ;
l = 51 ;
Bafta !