[tex] \sqrt{ \frac{20}{9} } - \sqrt{ \frac{100}{16} } + \sqrt{ \frac{81}{25} } = \frac{2 \sqrt{5} }{3} - \frac{10}{4} + \frac{9}{5} = \frac{2 \sqrt{5} }{3} - \frac{5}{2} + \frac{9}{5} = \frac{20 \sqrt{5}-75+54 }{30} [/tex]
=[tex] \frac{20 \sqrt{5} -21}{30} [/tex]
