1) [tex] \frac{1}{3}x+ \frac{1}{5}x=11 \\ \frac{5}{15}x+ \frac{3}{15}x=11 \\ \frac{8}{15}x=11 \\ x= \frac{11*15}{8}= \frac{165}{8} [/tex]
2)[tex]a+b=550 \\ a:b=17, r 10 \\ D=I*C+R \\ a=17b+10 \\ 17b+10+b=550 \\ 18b=540 \\ b=540:18=30 \\ a=17*30+10=510+10=520[/tex]