$U=64cmU=64cm$

$U=2a+2bU=2a+2b$

$U=2a+2(a+13\mathrm{c}\mathrm{m})=4a+26\mathrm{c}\mathrm{m}U=2a+2(a+13\backslash mathrm\{cm\})=4a+26\backslash mathrm\{cm\}$

$64\mathrm{c}\mathrm{m}=4a+26\mathrm{c}\mathrm{m}64\backslash mathrm\{cm\}=4a+26\backslash mathrm\{cm\}$ $\mid -26\mathrm{c}\mathrm{m}\backslash mid-26\backslash mathrm\{cm\}$ $\mid :4\backslash mid:4$

$a=\mathrm{9,5}\mathrm{c}\mathrm{m}a=9\{,\}5\backslash mathrm\{cm\}$

$b=a+13\mathrm{c}\mathrm{m}=\mathrm{22,5}\mathrm{c}\mathrm{m}b=a+13\backslash mathrm\{cm\}=22\{,\}5\backslash mathrm\{cm\}$