Help imi trebuie urgent

Răspuns:
a·3+3=30
3a=30-3=>a=27:3=>a=9
_________
(b+3)·3=30
b+3=30:3
b=10-3
b=7
___________
[(c-3):3]+3=30
(c-3):3=30-3
c-3=27·3
c=81+3
c=84