Subtract a+2b-3c from the sum of 2a+4b+7c and 2a-5b+3c
Sum of 2a+4b+7c and 2a-5b+3c
=(2a+4b+7c)+(2a-5b+3c)=2a+2a+4b-5b+7c+3c=4a-b+10c
Now,
=(4a-b+10c)-(a+2b-3c)=4a-b+10c-a-2b+3c=3a-3b+13c
From the sum of a+b-3cand b+c-a subtract the sum of 3c-8b+2aand -2c+5a-2b