**Add :**

**(i) 5a + 3b, a – 2b, 3a + 5b**

**(ii) 8x – 3y + 7z, -4x + 5y – 4z, -x – y – 2z**

**(iii) 3b – 7c + 10, 5c – 2b – 15, 15 + 12c + b**

**(iv) a – 3b + 3; 2a + 5 – 3c ; 6c – 15 + 6b**

**(v) 13ab – 9cd – xy ; 5xy ; 15cd – 7ab ; 6xy – 3cd**

**(vi) x ^{3} – x^{2}y + 5xy^{2} + y^{3 }; -x^{3} – 9xy^{2} + y^{3 }; 3x^{2}y + 9xy^{2}**

**(vii) a ^{6} – 4a^{4} + 6a ; 5a^{6} + 5a^{4} + 6a ; 12a^{6} – 10a**

**(viii) 2ax – 6by + 4cz, 4by – 14ax, 9cz – 4ax – 6by**