3(a+2)=4a I multiply 3*a+3*2=4a

Question

so 3a+6=4a I added 3a to 4a/ =7a
and answer was 1(answer is 6) i just don't understand how and why we subtract 3a from 4a instead of adding. please help me

Answer 1

You have got:
3a+6=4a
but we know that
3a =3a
So subtract one equation from the second,
3a+6-3a = 4a-3a
which gives
6 = a