Răspuns :
[ 12 + 3 × ( 2 × a + 1 ) ] = 24
3 × ( 2 × a + 1 ) = 24 - 12
3 × ( 2 × a + 1 ) = 12
2 × a + 1 = 12 : 3
2 × a + 1 = 4
2 × a = 4 - 1
2 × a = 3
a = 3 : 2
a = 1, 5 => numărul aflat
3 × ( 2 × a + 1 ) = 24 - 12
3 × ( 2 × a + 1 ) = 12
2 × a + 1 = 12 : 3
2 × a + 1 = 4
2 × a = 4 - 1
2 × a = 3
a = 3 : 2
a = 1, 5 => numărul aflat