x-numarul
{{[(x×2)+12]:2}-5}+7=9×3
{{[(x×2)+12]:2}-5}+7=27
{[(x×2)+12]:2}-5=27-7
{[(x×2)+12]:2}-5=20
[(x×2)+12]:2=20+5
[(x×2)+12]:2=25
(x×2)+12=25×2
(x×2)+12=50
x×2=50-12
x×2=38
x=38:2
x=19
PROBA
{{[(x×2)+12]:2}-5}+7=27
înlocuim pe x cu 19
{{[(19×2)+12]:2}-5}+7=
={[(38+12):2]-5}+7=
=[(50:2 )-5]+7=
=(25-5)+7=
=20+7=
=27 ( adevărat )