Verified answer

1) 5*3/5+7*4/7=3+4=7

5*4/7+7*3/5= 20/7+21/5= 100/35+147/35= 247/35= 7 2/35

3) 8a+3a-2-5a+2= 6a

7n+3m+8n-5m-10n+2m= 5n

6) a-(c-a-b)= a-c+a+b= 2a+b-c