[tex] \frac{a}{b} = 2 \: \: \: \: \: \: \: \: \: \: \: \frac{b}{a} = \frac{1}{2} \\ \frac{5b - a}{a} = \frac{5b}{a} - \frac{a}{a} = \frac{5b}{a} - 1 = \\ = \frac{5}{2} - 1 = 2 \frac{1}{2} - 1 = 1 \frac{1}{2} = 1.5[/tex]