[tex]\it \dfrac{a}{b}=\dfrac{5}{12} \Rightarrow b = \dfrac{12a}{5} \Rightarrow b = \dfrac{24a}{10} \Rightarrow b = 2,4a\ \ \ \ \ \ (*)
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\dfrac{a+b}{2a} \stackrel{(*)}{=} \dfrac{a+2,4a}{2a} = \dfrac{3,4a}{2a}=\dfrac{3,4}{\ 2} = 1,7 \\ \\ \\
\dfrac{a+2b}{5a-2b} = \dfrac{a+2\cdot2,4a}{5a-2\cdot2,4a} =\dfrac{a+4,8a}{5a-4,8a} = \dfrac{5,8a}{0,2a} =\dfrac{^{10)}5,8}{0,2}=\dfrac{58}{2}=29[/tex]
