Răspuns:
{[(a+3)x3+3]x3+3}x3+3=120
{[(a+3)x3+3]x3+3}x3=120-3
{[(a+3)x3+3]x3+3}x3=117
[(a+3)x3+3]x3+3=117÷3
[(a+3)x3+3]x3+3=39
[(a+3)x3+3]x3=39-3
[(a+3)x3+3]x3=36
(a+3)x3+3=36÷3
(a+3)x3+3=12
(a+3)x3=12-3
(a+3)×3=9
a+3=9÷3
a+3=3
a=3-3
a=3
Sper ca te-am ajutat!!!