Question

daca a+3b+18c=25 si b+6c=2, aflati a

Answer 1

 

$\displaystyle\bf\\a+3b+18c=25\\b+6c=2\\..................\\a+3(b+6c)=25\\b+6c=2\\..................\\\\a+3\times(2)=25\\a+6=25\\a=25-6\bf\\\boxed{\bf a=19}$