\[\boxed{\text{996.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ \frac{38^{2} - 17^{2}}{72^{2} - 16^{2}} =\]
\[= \ \frac{(38 - 17)(38 + 17)}{(72 - 16)(72 + 16)} =\]
\[= \ \frac{21 \cdot 55}{56 \cdot 88} = \ \frac{21 \cdot 5}{56 \cdot 8} = \frac{15}{64}\]
\[\textbf{б)}\ \ \frac{{39,5}^{2} - {3,5}^{2}}{{57,5}^{2} - {14,5}^{2}} =\]
\[= \ \frac{(39,5 - 3,5)(39,5 + 3,5)}{(57,5 - 14,5)(57,5 + 14,5)} =\]
\[= \ \frac{36 \cdot 43}{43 \cdot 72} = 0,5\]
\[\textbf{в)}\ \ \frac{{17,5}^{2} - {9,5}^{2}}{{131,5}^{2} - {3,5}^{2}} = \ \]
\[= \frac{(17,5 - 9,5)(17,5 + 9,5)}{(131,5 - 3,5)(131,5 + 3,5)} =\]
\[= \ \frac{8 \cdot 27}{128 \cdot 135} = \ \frac{27}{16 \cdot 135} =\]
\[= \ \frac{3}{16 \cdot 15} = \ \frac{1}{16 \cdot 5} = \frac{1}{80}\]