4)5целых 2/5*40/81*15/16=? 6)12целых6/7*2/25*7/18=? 8)3целых9/10*8/13*4целых1/6=?

[latex] 5\frac{2}{5}* \frac{40}{81} * \frac{15}{16} = \frac{27}{5}* \frac{40}{81} * \frac{15}{16} =\frac{27*40*15}{5*81*16}= \frac{10*3}{3*4}= \frac{10}{4}= \frac{5}{2}=2 \frac{1}{2} [/latex] [latex]12 \frac{6}{7}* \frac{2}{25}* \frac{7}{18}= \frac{90}{7}* \frac{2}{25}* \frac{7}{18}= \frac{90*2*7}{7*25*18}= \frac{90}{225}= \frac{18}{45} [/latex] [latex]3 \frac{9}{10}* \frac{8}{13}* 4 \frac{1}{6}= \frac{39}{10} * \frac{8}{13}* \frac{25}{6}= \frac{39*8*25}{10*13*9}= \frac{3*4*25}{5*9}= \frac{4*5}{3} = \frac{20}{3} = 6\frac{2}{3} [/latex]