apakah ada yang tau dari nomor ,10-12

11. [tex] \frac{11}{15} - \frac{2}{5} - \frac{3}{10} = \frac{22-12-9}{30} = \frac{1}{30} [/tex]
13. [tex]30 \sqrt{60} =0.5[/tex]
12. 10[tex] \frac{1}{2} = \frac{21}{2}[/tex]
       [tex] \frac{21}{2} x \frac{2}{3} = \frac{42}{6} = 7[/tex]
       sisa tali [tex] \frac{21}{2} - \frac{7}{1} = \frac{21-14}{7} = \frac{7}{2} [/tex]
       setengah tali yang dipakai [tex] \frac{7}{2} x \frac{1}{2} = \frac{7}{4} = 1\frac{3}{4} [/tex]