Ajutooor la 2 plssssss

Răspuns:
a+b+c= 12
Explicație pas cu pas:
2a+3b+4c=45
4a+3b+2c=27 / *2
a+b+c=??
8a+6b+4c= 54
2a+3b+4c=45
_______________
6a+ 3b=9 | :3
2a+ 1b=3
2a+3b+4c=45
3+ 2b+4c=45
2b+4c=42 |:2
1b+2c= 21
=> 2a+1b+1b+2c=21+3
2a+2b+2c=24 |:2
a+b+c= 12