Verified answer

[tex]a) \: \: \: \: \: \frac{a}{7} + \frac{3a}{5} = \frac{5a + 21a}{35} = \frac{26a}{35} \\ [/tex]

[tex]б) \: \: \: \: \: \frac{2a - 3}{4} + \frac{a - 5}{8} = \frac{2(2a - 3) + (a - 5)}{8} = \frac{4a -6 + a - 5}{8} = \frac{5a - 11}{8} [/tex]

[tex]в) \: \: \: \: \: \frac{4}{3x} + \frac{5}{5x} = \frac{20 + 15}{15x} = \frac{35}{15x} = \frac{7}{3x} \\ [/tex]

[tex]г) \: \: \: \: \: 3 + b - \frac{4b}{3 + b} = \frac{3(3 + b) + b(3 + b) - 4b}{3 + b} = \frac{9 + 3b + 3b + {b}^{2} - 4b }{3 + b} = \frac{ {b}^{2} + 2b + 9 }{3 + b} [/tex]

[tex]д) \: \: \: \: \: 4 - \frac{5}{3x} = \frac{12x - 5}{3x} \\ [/tex]

[tex]е) \: \: \: \: \: \frac{5}{ {ab}^{2} } - \frac{7}{ {a}^{2}b } = \frac{5a - 7b}{ {a}^{2} {b}^{2} } \\ [/tex]

[tex]ж) \: \: \: \: \: \frac{a + b}{ab} - \frac{a - c}{ac} = \frac{c(a + b) - b(a - c)}{abc} = \frac{ac + bc - ab + bc}{abc} = \frac{ac +2bc - ab }{abc} [/tex]

[tex]з) \: \: \: \: \: 1 - \frac{4a}{a - b} = \frac{a - b - 4a}{a - b} = \frac{ - 3a - b}{a - b} \\ [/tex]