[tex]\it\ a)\ \ \dfrac{x}{20} = \dfrac{^{4)}4}{\ 5} \Rightarrow \dfrac{x}{20}=\dfrac{16}{20}\Rightarrow x=16[/tex]
[tex]\it\ b) \ \ \dfrac{45}{y} =\dfrac{9}{5} \Rightarrow \dfrac{y}{45} = \dfrac{^{5)}5}{\ 9} \Rightarrow \dfrac{y}{45} = \dfrac{25}{45} \Rightarrow y = 25[/tex]
[tex]\it c)\ \ \dfrac{a}{6} = 13 \Rightarrow a = 6\cdot 13 \Rightarrow a = 78[/tex]
[tex]\it\ d) \ \ \dfrac{2}{3b} = \dfrac{10}{15} \Rightarrow \dfrac{3b}{2} = \dfrac{15}{10}^{(5} \Rightarrow \dfrac{3b}{2}=\dfrac{3}{2} \Rightarrow 3b=3 \Rightarrow b=1 .[/tex]
