Subtract a-2b-c from the sum of 3a-b+c and a+b-3c

Dear student
as per given equation 
Sum will be
3a-b+c +a+b-3c = 4a-2c -------(1)
now subtraction of give equation with (1)
4a-2c-a+2b+c= 3a+2b-c

=3a +2b-c is answer
Regards