Question 81 (vii)
Add :
3a(2b+5c),3c(2a+2b)
We have, 3a(2b+5c)+3c(2a+2b) =(6ab+15ac)+(6ac+6bc)=6ab+15ac+6ac+6bc [grouping like terms] =6ab+21ac+6bc
Question 81 (vi)
Add:
3a(a - b + c) , 2b(a - b + c)