[tex]\frac{2a}{5b}=0.7=\frac{7}{10} \\ \\ 20a=35b \ |:5 \\ \\ 4a=7b \\ \\ a=\frac{7b}{4} \\ \\ 2a+5b=34 \\ \\ 2*\frac{7b}{4}+5b=34 \\ \\ \frac{7b}{2}+5b^{(2}=34^{(2} \\ \\ 7b+10b=68 \\ \\ 17b=68 \\ \\ \boxed{b=4} \\ \\ a=\frac{7*4}{4} \\\\ \boxed{a=7}[/tex]
