[tex] \frac{4a + b}{3a - b} = 4[/tex]
[tex]4(3a - b) = 4a + b[/tex]
[tex]12a - 4b = 4a + b[/tex]
[tex]12a - 4a = b + 4b[/tex]
[tex]8a = 5b \: | \div 5b[/tex]
[tex] \frac{8a}{5b} = 1[/tex]
[tex] \frac{a}{b} = \frac{1}{\frac{8}{5} }[/tex]
[tex] \frac{a}{b} = \frac{5}{8} [/tex]
