[tex]7[/tex]

[tex]( {3a}^{2} b - {4ab}^{2} + b) - ( - {a}^{2} b - {3ab}^{2} + 5b) = {3a}^{2} b - {4ab}^{2} + b + {a}^{2} b + {3ab}^{2} - 5b = {4a}^{2} b - {ab}^{2} - 4b[/tex]

[tex]8[/tex]

[tex](35 {m}^{5} {n}^{4} - 10 {m}^{6}n {}^{5} + 5 {m}^{3} {n}^{4} ) \div (5 {m}^{3} {n}^{4} ) = \frac{5 {m}^{3} {n}^{4} (7 {m}^{2} - 2 {m}^{3} n) }{5 {m}^{3} {n}^{4} } = {7m}^{2} - {2m}^{3} n = {m}^{2} (7 - 2mn)[/tex]