Răspuns :
Fie x - numarul la care te gandesti
[(x : 5) * 2] : 4+5=9
[(x:5) * 2] : 4 = 4
(x : 5) * 2=4*4
(x : 5) * 2 = 16
x:5 = 16:2
x:5=8
x=8*5
x=40
[(x : 5) * 2] : 4+5=9
[(x:5) * 2] : 4 = 4
(x : 5) * 2=4*4
(x : 5) * 2 = 16
x:5 = 16:2
x:5=8
x=8*5
x=40
a = numarul la care ma gandesc
[ ( a: 5 ) x 2]: 4 + 5 = 9
[ ( a : 5 ) x 2 ] : 4 = 9 - 5
[( a : 5 ) x 2 ] : 4 = 4
[ ( a : 5 ) x 2 ] = 4 x 4
[ ( a : 5 ) x 2 ] = 16
( a : 5 ) = 16 : 2
a : 5 =8
a = 8 x 5
a = 40
[ ( a: 5 ) x 2]: 4 + 5 = 9
[ ( a : 5 ) x 2 ] : 4 = 9 - 5
[( a : 5 ) x 2 ] : 4 = 4
[ ( a : 5 ) x 2 ] = 4 x 4
[ ( a : 5 ) x 2 ] = 16
( a : 5 ) = 16 : 2
a : 5 =8
a = 8 x 5
a = 40