[tex]a) \frac{5}{3} = \frac{15}{x} [/tex]
[tex]x = \frac{3 \times 15}{5} = 3 \times 3 = 9[/tex]
[tex]b) \frac{2}{7} = \frac{x + 1}{2x + 8} [/tex]
[tex]2(2x + 8) = 7(x + 1)[/tex]
[tex]4x + 16 = 7x + 7[/tex]
[tex]4x - 7x = 7 - 16[/tex]
[tex] - 3x = - 9 \: | \div ( - 3)[/tex]
[tex]x = 3[/tex]
